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SC-FDMA for 3GPP LTE uplink
Hong-Jik Kim, Ph. D.
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Wireless Broadband – The New Category
ile 3GPP LTEUMTS / M
obil
HSDPA
3GPP LTE
802.20
WCDMACellular Wireless Broadband
Are
a
1xEV-DO WiMAX 802.16e
WiFi 802 11
Loca
l A
802.11 a/b/g
WiFiCordless 802.11 n
ed
a/b/gWiMAX 802.16d
NG –DSLDSL / Cable /
Fixe DSL
/ DLCPOTSDSL / Cable /
Fiber
Existing 2004-2006 Rollout 2006+
Voice & Messaging Broadband
Hong-Jik Kim2
Existing 2004-2006 Rollout 2006+
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3GPP Standard
J PDC
2G2G 2,5G2,5G 3G3G 3,5G3,5G 4G ?4G ?
Japan
Europe
PDC
GSM GPRS WCDMA HSDPA LTEHSUPA Rel. 7Europe
North
GSM
TDMA
GPRS R99 Rel. 5
EDGE
LTERel. 6 Rel. 6
DL Shared CH
UL Shared CH
Multi-CarrierDL MIMO
OFDMADL/UL MIMOAmerica TDMA EDGE S a ed C
HARQAMC
S a ed CHARQAMC
O DL/UL MIMO
Hong-Jik Kim3
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3GPP LTE objectives> Scalable bandwidth : 1.25, 2.5, 5, 10, (15), 20MHz
> Peak data rate (scaling linearly with the spectrum allocation)• DL (2 Rx @ UE) : 100Mb/s for 20MHz spectrum allocation• UL (1 Tx @ UE) : 50Mb/s for 20MHz spectrum allocation
> Spectrum efficiency> Spectrum efficiency• DL : 3-4 times HSDPA for MIMO (2,2)• UL : 2-3 times HSUPA for MIMO(1,2)
> Reference Antenna configurations (targets)• DL : 2Tx and 2 Rx• UL : 1 Tx and 2 Rx
> Latency• C-plane : < 50-100ms to establish U-plane
U plane < 10ms from UE to ser er• U-plane : < 10ms from UE to server
> Capacity• 200 users for 5MHz, 400 users in larger spectrum allocations (active state) g p ( )
> Mobility• LTE is optimised for low speeds 0-15km/h but mobility is maintained for speeds up to 350km/h
Hong-Jik Kim4
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OFDMANu Nc Nc Np+Nc
S/P converter
Constellation mapping Symbol
toSubcarrier
Nc-pointIFFT Cyclic P/S
Bit Stream
Mapping Prefix converter
> High PAPRg• Need for PAPR reduction scheme especially for UL
> Various mappings from Nu data symbols to Nu subcarriers> Various mappings from Nu data symbols to Nu subcarriers among Nc subcarriers
> Receiver is based on FFT
Hong-Jik Kim5
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OFDM / MIMO> OFDM – robust in dense environments> OFDM / MIMO perfect long term marriage> Achieves considerable increase in capacity peak rates> Achieves considerable increase in capacity, peak rates
& coverage
Space TimeQAMSymboler
1A
r
1 A’na
Space-TimeSymbol Multi-Element
Receiver-
er1
r
’
-Multi-Element Transmitter
-x
Enco
de
.
.
.
.
.
.
.
BC
MIMOChannel Matrix, H
t0 t1 t2 Dec
oder
.
.
B’C’
.
.
.
.
.
TxA
nten
x En
cod e
.
.
.
.
.
.
.
.
.
MIMOChannel Matrix, H
MIMOChannel Matrix, H
t0 1 t2 Dec
oder
.
.
.
.
’’
.
.
.
.
.
‘Space-Time Codeword’
Tx. .
NT Rx .
NR‘Space-Time Codeword’
Tx.. .
T Rx ..
R
2.5GHz, 10MHz,TDDMIMO (Tx:Rx) 1x1 1x2 2x2 2x4 4x2 4x4Bits/Sec/Hz/Sector 1 2 1 8 2 8 4 4 3 7 5 1
OFDMA
Cornerstone Technology for WiMAX, 3GPP LTE, 3GPP2 Evol and 802.20P ti l D l t ith 2X4 C fi ti C bl & A t S l ti
Bits/Sec/Hz/Sector 1.2 1.8 2.8 4.4 3.7 5.1
Hong-Jik Kim6
Practical Deployments with 2X4 Configurations – Cable & Antenna Solutions
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UL: Single Carrier (SC)-FDMA
> DFT-spreading of data symbols in frequency domain
> Low PAPR> Subcarrier mapping
• Distributed mapping• Frequency diversity• Frequency diversity• Transmit signal similar to IFDMA
• Localized mapping• Multi user diversity (frequency domain scheduling)• Multi-user diversity (frequency domain scheduling)• transmit signal similar to narrowband single-carrier
> MMSE equalization to restore code orthogonality
Hong-Jik Kim7
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UL: Interleaved FDMA (IFDMA)kt
Tj
eπ2
can be used by different users
> Also known as distributed SC-FDMA
comb-shaped spectrum
> Also known as distributed SC FDMA
> Hybrid of single-carrier and OFDM concepts• Low PAPR (same as single carrier)Low PAPR (same as single carrier)
> Orthogonal uplink as each user is assigned set of sub-carriers orthogonal to other users
> Receiver is based on FDE (e.g. MMSE).
Hong-Jik Kim8
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Localized vs. Distributed
5/4 = 1.25 MHz LocalizedLarger frequency diversity
L t d hi h t i t
Less frequency diversityHigher FER for narrowband users
5 MHz Distributed, RF = 4
Low-rate and high-rate users coexist peacefully
Time domain channel has less power
Higher FER for narrowband usersTime domain channel has larger power fluctuations
Difficult to choose appropriate MCS due to Time domain channel has less power fluctuation
More stable MCS selectionM t t l
Difficult to choose appropriate MCS due to rapid channel fluctuationsLess accurate power control
Low-rate user may block a high-rate More accurate power control
Channel estimation becomes degraded for very large repetition factors
Low rate user may block a high rate (broadband) user from the channel, especially if channel dependent scheduling is used for very large repetition factors
Tighter frequency synchronization may be required
g
Narrowband filter has longer impulse response reduces “effective” CP length (IFDMA only)length (IFDMA only)
Channel estimation not degraded at low bandwidths
Hong-Jik Kim9
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Frame structure
SB
1 sub-frame = 0.5 msec
SB
1 b f 0 5
CP LB#1 CPCP SB#1 LB#6CP LB #2 CP LB #3 CP LB #4 CP LB #5 CP SB
#2
> 1 sub-frame = 0.5ms• 6 LB (Long Block) for user / control data transfer
2 SB (Sh t Bl k) f il t / t l d t t f• 2 SB (Short Block) for pilot / control data transfer
Hong-Jik Kim10
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Cluster structure, Localized FDMA
10 data sub-carriers + 5 pilot sub-carriers
1 h t bl k
1 long block
1 short block
1 TTI1 long block
Data sub-carrier
Pilot sub-carrier
Unobserved sub-carrier short blocks
Hong-Jik Kim11
Unobserved sub-carrier, short blocks
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Cluster structure, Interleaved FDMA
10 data sub-carriers + 5 pilot sub-carriers per user
1 TTI
Data sub-carrier of user 1, 2 ,3 ,4
Unobserved sub-carrier short blocks
Pilot sub-carrier of user 1, 2 ,3 ,4
Hong-Jik Kim12
Unobserved sub carrier, short blocks
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Simulation Parameters
Frequency hopping used on a TTI basisMCS: QPSK rate ¼, ½, ¾ & 16 QAM rate ½, ¾ 1 transmit, 2 receive antennas (uncorrelated)ITU PB channel@3 km/hrOne turbo block per TTITTI=0.5msBoth ideal and estimated channel running side by sideBoth ideal and estimated channel running side by sidePilot overhead: 1/7Sampling Rate = 15 359 MHz (=4*3 84MHz)Sampling Rate = 15.359 MHz (=4 3.84MHz)Pilot power boost = 3dB (i.e. pilot signal amplitude = sqrt(2)*data signal amplitude) QPSK modulation with constant modulus in thesignal amplitude), QPSK modulation with constant modulus in the frequency domain.
Hong-Jik Kim13
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Results for Loc.FDMA, v=3km/h
100
Loc.FDMA, v=3km/h
10-1
LER
10-2
BL
QPSK 1/4, Perfect IR10
QPSK 1/4QPSK 1/2, Perfect IRQPSK 1/2QPSK 3/4, Perfect IRQPSK 3/4QPSK 3/416QAM 1/2, Perfect IR16QAM 1/216QAM 3/4, Perfect IR16QAM 3/4
Hong-Jik Kim14
-10 -5 0 5 10 15 2010
-3
SNR
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Results for IFDMA , v=3km/h
100
iFDMA, v=3km/h10
0
-110
-1
R
2
BLE
R
10-2
QPSK 1/4, Perfect IRQPSK 1/4QPSK 1/2, Perfect IRQPSK 1/2QPSK 3/4 Perfect IRQPSK 3/4, Perfect IRQPSK 3/416QAM 1/2, Perfect IR16QAM 1/216QAM 3/4, Perfect IR16QAM 3/4
Hong-Jik Kim15
-15 -10 -5 0 5 10 15 2010
-3
SNR
16QAM 3/4
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iFDMA/Loc.FDMA with real channel estimation , v=3km/h
100
SUBBAND/DIVERSITY, Estimated channel, v=3km/h10
0
-110
-1
R
2
BLE
R
iFDMA QPSK 1/410-2 iFDMA QPSK 1/4
Loc.FDMA QPSK 1/4iFDMA QPSK 1/2Loc.FDMA QPSK 1/2iFDMA QPSK 3/4Loc.FDMA QPSK 3/4iFDMA 16QAM 1/2Loc.FDMA 16QAM 1/2iFDMA 16QAM 3/4Loc.FDMA 16QAM 3/4
Hong-Jik Kim16
-15 -10 -5 0 5 10 15 2010
-3
SNR
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Th kThank you