Mobile Wimax 802.16e Phy 02

8/2/2019 Mobile Wimax 802.16e Phy 02

http://slidepdf.com/reader/full/mobile-wimax-80216e-phy-02 1/21

Mobile WiMAX Release 1 (IEEE 802.16e):

Director WiMAX Standards,Vice Chair, IEEE ® 802.16 Working Group for

Broadband Wireless Standards, Mobile Wireless Group, Intel ® Corporation

Email: [email protected]

15/17/2010 Copyright Intel Corporation © 2009Copyright Intel Corporation © 2009

twitter: JosePuthenkulam



o e e ease . eOFDMA Physical Layer Aspects

•Broadband Channel Challenges

•OFDMA Basics

•OFDMA Frame Structure•Subchannelization (Permutations), Zones•Adaptive Modulation

• y‐•Smart Antennas: MIMO, Beamforming

•Mobile WiMAX System Profile PHY features

25/17/2010



Broadband Channel Challenges

Frequency variation:

• Multipath delay spread at

Receiver

Time variation:

•

35/17/2010



OFDMA Signal

• : rt ogona requency v s on u t p e ccess

– Available bandwidth is divided into N (large number of) orthogonal sub‐carriers

– Each sub‐carrier individuall modulated AM at 1 N total data rate

– FFT implementation

(fast

and

efficient)

– Subcarrier level multiple user access• prov es n erent res stance to mu t ‐pat

– Each sub‐carrier (narrowband) incurs flat fading (app.)

– Low data

rate

per

sub

‐carrier

‐‐> low

intersymbol interference

ISI– Use of cycle prefix guard interval (with GI > max delay spread)

• No inter‐symbol interference

• Retains sub‐carrier orthogonality

w e r

45/17/2010

P



OFDMA and Multipath Performance

……

PathsPaths

Previous Symbol Present Symbol

Area of ISI

BaseBase

……

Time

Echo ofPrevious

SubscriberSubscriberStationStation

• Signals follow several propagation paths

Symbol

• Multiple copies of signal arrive at the receiver, offset in time

– Signal distortion and inter-symbol interference (ISI)

• a ng anne– Frequency selective fading (delay spread)

– Time selective fading (Do ler)

55/17/2010



OFDMA: Orthogonal Frequency Division Multiple Access

• Users/bursts are scheduled across both frequency

(sub‐channels) and time (symbols)

–

,

– Higher granularity in resource allocation– More degrees of freedom in scheduling–

65/17/2010



Subchannelization

Active sub-carriers are divided into subsets called sub-channels.

Guar d Bands

Su b - ch a n n el # 1

DC Sub -car r ierSu b - ch a n n e l # N

Guar d Bands

u scr er may e ass gne one or more su -c anne s, severa su scr ers may transm t s mu taneous y g ercapacity & better QoS

Subchannelization Gain

– If subscriber uses only one subchannel it concentrates all transmitting power in the subchannel additional link margin on uplink

Num ber o f UL Subchanne ls

M a x i m u mUL Subchan ne l iza t io n Gain

( d B )

FFT PUSC

slo t ) PUSC

s lo t )

512 17 24 12.3 13.8

1024 35 48 15.4 16.8

75/17/2010

7



OFDMA Structure

•Pilots used for channel estimation and trackin

•Interleaving (bits distributed across tones) and error correcting facilitates

recovery under frequency selective fading or narrow-band interference

85/17/2010 88



TDD vs. FDD: Frame Structure

Time-Division Duplex (TDD)• DL & UL time-share the same RF channel

• Dynamic asymmetry

Frequency-Division Duplex (FDD)• Downlink and Uplink on separate RF channels

• Static asymmetry

• -• oes no ransm rece ve s mu aneous y

(low cost)•HFDD MS does transmit/receive simultaneously

y

UL Subframe

DL Subframe

FDD

DL Frequency F1

UL Frequency F2 F r e q u e n

Frame n-1 Frame n Frame n+1 Frame n+2

Time

u rame u rame

DL Timeslot T1

TDDUL Timeslot T1

95/17/2010

UL=Uplink, DL=Downlink, MS=Mobile Station



TDD vs. FDD Comparison

• TDD Advanta es

– Enables asymmetric

bandwidth

usage

– Allows flexible bandwidth split between uplink and downlink

–

efficient set of MIMO techniques

– TDD transceiver

design

is

cheaper

and

less

complex

• FDD Advantages– Some regulators allocated only FDD spectrum

– TDD and FDD do not mix well

– Easier coexistence

with

existing

technologies

and

between

operators (no need for network sync)

105/17/2010



OFDMA Frame Structure (TDD)SS

S+1S+1S+2S+2

FCHFCH

D L D L - - M A P

M A P

UL Burst #1UL Burst #1

Q I C H s

Q I C H s

FCHFCH

l N u m b e r

l N u m b e r

M A P

M A P

DL Burst #3DL Burst #3

K C H s

K C H s

h a n n e l s L o g i c

h a n n e l s L o g i c

U L U L - -


Burst #4Burst #4

ULUL Burst #2Burst #2

n g n g

A A

S u b

S u b

E A M B L E

E A M B L E

- - M A P

M A P


DLDLBurst #5Burst #5

E A M B L E

E A M B L E

ULUL Burst #3Burst #3 M A R a n g i

M A R a n g i

i o d i c R a n g i n

i o d i c R a n g i n

n d i n g

n d i n g

S+LS+L

Time – OFDMA Symbols (Ts)

P P D Dkk

k+1k+1 k+3k+3 k+ik+i

P P C C P e P e

S o S o

115/17/2010

RTGRTGTTGTTGDLDL ULUL

QPSK

1/2

16QAM

3/4

64QAM

3/4

64QAM

2/3

16QAM

1/2

QPSK

¾

QPSK

1/4

Possible

Modulations



Multi‐zone Frame Structure

• Each zone can have different permutation

• Each

zone

can

have

di erent

requency

reuse• Zone can be configured frame‐ by‐frame

125/17/2010



MBS and HARQ Zones

1st PUSC Zone PUSC STC Zone MBS PUSC STC Zone PUSC Zone

N G I N G

F C H

1st PUSC Zone PUSC STC Zone MBS PUSC STC Zone PUSC Zone

N G I N G

F C H

1st PUSC Zone PUSC STC Zone MBS PUSC STC Zone PUSC Zone1st PUSC Zone PUSC STC Zone MBS PUSC STC Zone PUSC Zone

N G I N G

F C H

R A

A C K

M B L E

M B S

M A P

MBS H-ARQH-ARQREGION

COMPRESSED

R A

A C K

M B L E

M B S

M A P


COMPRESSED

R A

A C K

M B L E

M B S

M A P


COMPRESSED

C Q I C H

P R E A REGION

(VoIP)

(VoIP)

C Q I C H

P R E A REGION

(VoIP)

(VoIP)

C Q I C H

P R E A REGION

(VoIP)

(VoIP)

DL Sub-Frame UL Sub-FrameDL Sub-Frame UL Sub-FrameDL Sub-Frame UL Sub-Frame

• Frame partitioned

into

multiple

zones

in

time

• Different subchannelization scheme/application can be

135/17/2010

supporte

Source: WiMAX Forum Whitepaper



802.16 Adapts Modulation for Each Subscriber

145/17/2010

1 4



Smart Antennas : MIMO & Beamformingece ve pa a vers y

– Reduce fade margin, improve link budget

Transmit Spatial Diversity STC (Space time code)

– Reduce fade margin

2x1 STC

– Higher level modulation for same SINR

Downlink Spatial Multiplexing (SM)

– Improve capacity by transmitting parallel

2x2 Spatial Multiplexing Uplink Collaborative (Virtual) MIMO

– Improves uplink capacity by simultaneous

uplink transmission from 2 different users

x eam orm ngBeamforming

– Improve link budget

– Reduce interference

Smart antennas increase covera e and ca acit &

155/17/2010

are key enablers of continued wireless advancement



Transmit Spatial Diversity (STC)

Serial to Tx DiversityIFFT DAC / RF[S0 , -S1*]

Tx 1

IFFT DAC / RF[S1 , S0*] Tx 2

Diversity

CombiningRx

-

Transmit diversity requires extra antenna at the BS instead of the MS

Lower-cost subscriber terminal

165/17/2010



MIMO Spatial Multiplexing (SM)• Multiple Input Multiple Output (MIMO)

• Multiple antennas at both transmitter and receiver

• MIMO uses multipath to advantage to multiply data rate

• ransm s eren a a a ong eren pa s s mp e v ew

• MxN MIMO can

multiply

data

rate

by

M

or

N

(whichever

is

less)

if

there

is

enough multipath.

• Best in urban hi h‐multi ath environment and indoors

• Less effective in suburban and rural low‐multipath environments

Multi-Antenna Transmitter Multi-Antenna Receiver

c o d e r

M a p p i n g

c o d e r

IFFT

IFFT

M I M O E

M I M O S u b - c

.

.

.

.

.

.

.

.

.

M I M O D e

F FIFFT

IFFT

175/17/2010



UL Collaborative MIMO (Virtual MIMO)

• Multiple MSs transmit simultaneously creating a “virtual” multi‐antenna

transmitter

• MSs have one or two antennas, BS has multi le antennas

• Increased network capacity

Multiple Single-AntennaTransmitters

Multi-AntennaReceiver

r

MIMO Encoder IFFTMS1MS1

.

.

.

.

.

.

.

.

.

M O D e c o d

F F T

MIMO Encoder IFFT

MIMO Encoder IFFTMSMS22

M

I

MIMO Encoder IFFTMS4MS4BSBS

185/17/2010



Beamforming

• Narrow directed beam with higher antenna gain

• Reduce interference to and from other sectors and cells

• Null interferers

• Improves channel capacity & spectral efficiency

• Base station only (Tx and Rx)

195/17/2010



Mobile WiMAX Rel. 1 Profile (PHY)*

D u p le x i n g a n d Ch a n n elBandw id ths ( M Hz)

TDD

10 MHz: 10 24 FFT, 5 MHz: 5 12 FFT

8.75 MHz: 1024 FFT ( For Kor ea WiBro)

Fr am e Size, Cycl ic

Pre f ix

5 m s ec, 1 / 8

Sub-ca r r ie r A l loca t ionMode

Dow nl in k : PUSC, FUSC, AMC

,

Er r or Cor r ec t ion Codes& HARQ

CC Tai l B it i ng w / o H-ARQ

CTC w i th Chase Com b in ing H-ARQ or w / o H-ARQ

Modu lat ion Dow n l in k : QPSK, 1 6 QAM, 6 4 QAM

Upl in k : QPSK, 16QAM

Up l in k Co n t r o l ch a n n el s Ra n g in g ( I n i t i al : 2 sy m b o l , Pe r io d i c: 1 sy m b o l)

CQI CH ( enh anced) , ACKCH

ow n n : x sw c e u s n g

Up l ink : 1x 2 V i r t ua l SM (2 use rs mu l t i p lex ed) u s ing PUSC

Beam For m in g Usin g PUSC o r AMC in STC zon e

UL chann e l soun d in g

205/17/2010 * Snapshot of important features. Not exhaustive list. Please refer WiMAX Forum Specifications.

no AAS Zone sup por t



Mobile WiMAX Physical Layer Summary

• OFDMA Physical Layer is Optimized for Mobile

‐

Robust against frequency‐selective fading

Frequency, Space

and

Time

Diversity

Multi‐user access And Efficient Scheduling

Support of Smart Antennas

TDD advantages

215/17/2010

Documents

Mobile Wimax 802.16e Phy 02