080123 3 OFDM(a) Competence Development PartIII Final

8/13/2019 080123 3 OFDM(a) Competence Development PartIII Final

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OFDM Competence Development

2

Outline

Part I: What is OFDM?

Part II: Introducing multiple access: OFDMA, SC-FDMA

Part III: Wireless standards based on OFDMA

Part IV: Radio planning of OFDMA


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Wireless standards

Mobile WiMAX

3GPP Evolved UTRA

Basic OFDMA parameters

Resource mappings andscheduling

Multi-antenna support

Comparison

Other standards which useOFDM / OFDMA:

3GPP2 Ultra Mobile Broadband(UMB)

WLAN, 802.11a, .11g, .11n

Terrestrial Digital Broadcast:DVB-T, DVB-H


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Mobile WiMAX R1IEEE 802.16e

Based on the air-interface of IEEE 802.16e-2005

Amendment to Fixed WiMAX IEEE 802.16-2004

Adopted by ITU-R as member of the IMT-2000 family at RA-07as OFDMA TDD WMAN

WiMAX Release 1 ready since 2006

Scalable OFDMA. Bandwidth support: 5, 7, 8.75 and 10 MHz

Multi-antenna support (MIMO)

Expected peak data rates:

72 Mb/s combined (TDD UL+DL); BW = 10 MHz, MIMO 2x2

First working products in 2008


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Basic parameters for Mobile WiMAX

Supported system

bandwidths [MHz]

1.25 5 10 20 7 8.75

Sub-carrier frequencyspacing, f[kHz]

10.94 7.81 9.77

Useful symbol time, TU[s]

91.4 128.0 102.4

Cyclic prefix/Guard time,TCP[s]

11.4 16.0 12.8

Guard time overhead,TCP/(TCP+TU) [%]

11.1

Sampling frequency, fs[MHz]

1.4 5.6 11.2 22.4 8.0 10.0

FFT size, NFFT 128 512 1024 2048 1024 1024

Occ. Sub-carriers (PUSC) 360/272 720/560

Resource mapping Distributed or contiguous

Duplex methods TDD only

Modulation schemes QPSK, 16-QAM, 64-QAM - adaptive

Coding schemes

1/2, 2/3, 3/4, 5/6 rate convolutional code1/2, 2/3, 3/4, 5/6 rate convolutional turbo code

x2, x4, x6 repetition code

Multi-antenna support Yes


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Resource mapping for Mobile WiMAX

Diversity permutations (Distributed mappings):

DL-FUSC Fully Used Sub-Carrier

DL-PUSC, UL-PUSC Partially Used Sub-Carrier

DL-TUSC Tile Usage of Subcarriers

Contiguous permutation (Localized mapping):

Band AMC Adaptive Modulation and Coding


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Mobile WiMAX DL PUSC

Downlink Partially Used Sub-Carriers

Clusters of 14 contiguous SCs and two symbol intervals

Re-arranged to 6 groups

Permutation within each group to form sub-channels with 28 subcarriers (24 data + 8pilot)

Obtains diversity gain over the whole bandwidth


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Mobile WiMAX DL PUSC - explored

PPP

P

Frequency

Physical mapping

Logical mapping

Cluster: 14 SC x 2 symbols

30 clusters/420 SCs

Major group: 10 clusters/120 data SCs

Logical sub-channel/24 data SCs from a group

Sub-carr ier mapp ing

Cluster renum bering

DL-PUSC, NFFT

= 512


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Mobile WiMAX UL PUSC

Uplink Partially Used Sub-Carrier

Tiles of 4 contiguous SCs and 3 symbol intervals

Re-arranged to 6 groups

Permutation within each group to form sub-channels with 28 subcarriers(24 data + 8 pilot)


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3GPP Evolved UTRA LTE

Long Term Evolution (LTE). 4G technology from 3GPP.Standard more or less finalized in 2007

Scalable OFDMA. Bandwidth support from 1.4 20 MHz

SC-FDMA on the uplink

Multi-antenna support (MIMO)

Expected data rate above 100 Mb/s DL, 50 Mb/s UL; BW= 20 MHz, 2x2 MIMO

Pilot tests in 2007/8, first products in 2009/10


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Basic parameters for E-UTRA

Supported systembandwidths [MHz]

1.4 1.6

(TDDonly)

3 3.2

(TDDonly)

5 10 15 20

Sub-carrier frequencyspacing, f[kHz]

15 (7.5)

Useful symbol time, TU[s] 66.67 (133.33)

Cyclic prefix/Guard time,TCP[s]

Normal CP: 5.21/4.69Extended CP: 16.67

Guard time overhead,TCP/(TCP+TU) [%]

Normal CP: 6.67Extended CP: 20.0

Sampling frequency, fs[MHz]

7.68 15.36 23.04 30.72

FFT-size, NFFT 512 1024 1536 2048

Occ. subcarriers 72 84 180 192 300 600 900 1200

Resource mapping Distributed or contiguous

Duplex methods FDD and TDD

Modulation schemes QPSK, 16-QAM, 64-QAM, adaptive

Coding schemes 1/3 rate tail-biting convolutional code1/3 rate Turbo code

Multi-antenna support Yes


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Resource mapping for E-UTRA

Time-frequency resources are organised in Resource blocksspanning 12 SC x 7 symbol intervals (180 kHz x 0.5 ms)

Diversity permutation is by mapping virtual resource blocks tophysical resource blocks

Uplink is always localized mapping using SC-FDMA


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E-UTRA frame structures

DL

symbN OFDM symbols

0l 1DL

symb Nl

RB

sc

N

subcarriers

Resource

block

Resource element:

One time-frequency symbol

Frequency

Time

Symb#0 Symb#1 Symb#2 Symb#3 Symb#4 Symb#5 Symb#6CP0 CP1 CP2 CP3 CP4 CP5 CP6

Slot: 0.5 ms

#0 #1 #2 #3 #19#18

One radio frame, Tf = 307200Ts = 10 ms

One slot, Tslot = 15360Ts = 0.5 ms

One subframe

Frame structure type 1 (FDD)


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Multi-antenna support

Beamforming

Multiple antennas are used to transmit or receive weighted signals to improvecoverage and capacity

Space-Time Coding (STC)

Transmit diversity such as Alamouti coding to provide spatial diversity and reducefading margin

Spatial Multiplexing (SM) - MIMO

Higher peak rates and increased throughput. Multiple streams are transmitted overmultiple antennas. The receiver must also have multiple antennas to separate thedifferent streams.

E-UTRA

Baseline configuration: 2x2 (DL)1x2 (UL)

Mobile WiMAX

Minimum requirements, Wave II: 2x2 (DL), 1x2 (UL)

Reference signal (pilot) positionsidentify the different Tx antennas


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E-UTRA vs. Mobile WiMAX

Sub-carrier distance and usefulsymbol time

E-UTRA more robust to Doppler

Cyclic prefix/guard interval

Mobile WiMAX more robust to multipathdelays

Extended CP of E-UTRA an option for longdelays

Bandwidth support Basically same

Complexity

Similar

No clear winner when it comes toperformance on the physical layer

Migration and co-existence

E-UTRA is taylored to ease co-existencewith and migration from WCDMA/HSPA

Df= 15 kHz

Df= 10.94 kHz

TCP 5 ms T

U= 66.67 ms

TCP

= 11.4 ms TU

= 91.4 ms

E-UTRA

Mobile WiMAX

Frequency Time


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Mobile WiMAX R2 IEEE 802.16m

Completed Q4/07 ?

System profile R2 in 2008 ?

Bandwidth support: 5, 10, 20, 40 MHz

Peak data rates (requirements)

DL: > 350 Mb/s, 4x4 MIMO

UL: > 200 Mb/s, 2x4 MIMO

Average throughput per sector, BW = 20 MHz

DL: > 40 Mb/s

UL: > 12 Mb/s

Mobility support up to 350 km/h


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Ultra Mobile Broadband (UMB)

Next generation mobile broadband access from 3GPP2

Evolution from cdma2000 EV-DO Rev. C

Published September 2007

Bandwidths: 1.25 2.5 5 10 20 MHz

Number of subcarriers: 128, 256, 512, 1024, 2048 (FFT size) Subcarrier spacing: 9.6 kHz

Useful symbol duraton: 104.17 ms

Cyclic prefix duration: 6.51, 13.02, 19.53, or 26.04 ms

Windowing guard interval: 3.26 ms

Modulation: QPSK, 8-PSK, 16-QAM, 64-QAM, hierarchicalmodulation


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Wi-Fi, IEEE 802.11

WLAN standards 802.11a, g and n uses OFDM

Multiple access is not OFDMA but CSMA (TDMA variant)

Channel bandwidth: 22 MHz

Number of subcarriers: 52

Subcarrier spacing: 312.5 kHz

Useful symbol length: 3.2 ms

Guard interval (cyclic prefix): 0.8 ms

Modulation: BPSK, QPSK, 16-QAM, 64-QAM


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Summary - standards

Major future mobile broadband standards employ OFDMA

Mobile WiMAX, E-UTRA, UMB

Bandwidths are scalable

Flexible multi-user access

Multiple antennas (MIMO) supported

OFDM transmission is employed in several wirelessstandards

Fixed and nomadic wireless broadband: Wi-Fi, Fixed WiMAX

Digitial terrestrial broadcast: DVB-T, DVB-H

Documents

080123 3 OFDM(a) Competence Development PartIII Final