PERFORMANCE EVALUATION OF MOBILE WIMAX IEEE 802.16E FOR HARD HANDOVER
Mobile Wimax 802.16e Phy 02
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Transcript of 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
8/2/2019 Mobile Wimax 802.16e Phy 02
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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
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Broadband Channel Challenges
Frequency variation:
• Multipath delay spread at
Receiver
Time variation:
•
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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
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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
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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–
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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
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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
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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
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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)
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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 - -
DL Burst #1DL Burst #1
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
DL Burst #2DL Burst #2
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
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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
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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
MBS H-ARQH-ARQREGION
COMPRESSED
R A
A C K
M B L E
M B S
M A P
MBS H-ARQH-ARQREGION
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
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802.16 Adapts Modulation for Each Subscriber
145/17/2010
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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
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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
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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
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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
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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
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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
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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