Transcript Wireless standards based on OFDMA

OFDM(A) Competence Development – part III
Per Hjalmar Lehne, Frode Bøhagen, Telenor R&I
R&I seminar, 23 January 2008, Fornebu, Norway
[email protected]
[email protected]
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
•
Other standards which use
OFDM / OFDMA:
•
3GPP Evolved UTRA
•
Basic OFDMA parameters
– WLAN, 802.11a, .11g, .11n
•
Resource mappings and
scheduling
– Terrestrial Digital Broadcast:
DVB-T, DVB-H
•
Multi-antenna support
•
Comparison
– 3GPP2 Ultra Mobile Broadband
(UMB)
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Mobile WiMAX R1– IEEE 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-07
as “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 frequency
spacing, Df [kHz]
10.94
7.81
9.77
Useful symbol time, TU
[ms]
91.4
128.0
102.4
Cyclic prefix/Guard time,
TCP [ms]
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
360/272
720/56
0
Occ. Sub-carriers (PUSC)
Resource mapping
Duplex methods
Modulation schemes
Coding schemes
Multi-antenna support
Distributed or contiguous
TDD only
QPSK, 16-QAM, 64-QAM - adaptive
1/2, 2/3, 3/4, 5/6 rate convolutional code
1/2, 2/3, 3/4, 5/6 rate convolutional turbo code
x2, x4, x6OFDM
repetition
code
Competence Development
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 + 8
pilot)
Obtains diversity gain over the whole bandwidth
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Mobile WiMAX DL PUSC - explored
Frequency
P
P
P
P
Cluster: 14 SC x 2 symbols
30 clusters/420 SCs
Physical mapping
Cluster renumbering
Major group: 10 clusters/120 data SCs
Logical mapping
Sub-carrier mapping
Logical sub-channel/24 data SCs from a group
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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Mobile WiMAX frame structure
•
Mobile WiMAX currently supports Time Division Duplex (TDD)
– 802.16e also supports Frequency Division Duplex (FDD), Full- and halfduplex operation
•
All permutation schemes can be supported in each frame
•
DL PUSC is mandatory in first ”zone”
AMC
PUSC
(Guard interval)
TUSC
AMC
PUSC
FUSC
PUSC
(FCH, MAP)
Preamble
DL
UL
Frame length: 48 OFDMA symbols/5 ms
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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 system
bandwidths [MHz]
1.4
1.6
3
(TDD
only)
3.2
5
10
15
20
(TDD
only)
Sub-carrier frequency
spacing, Df [kHz]
15 (7.5)
Useful symbol time, TU
[ms]
66.67 (133.33)
Cyclic prefix/Guard time,
TCP [ms]
Normal CP: 5.21/4.69
Extended CP: 16.67
Guard time overhead,
TCP/(TCP+TU) [%]
Normal CP: 6.67
Extended CP: 20.0
Sampling frequency, fs
[MHz]
7.68
15.36
23.04
30.72
FFT-size, NFFT
512
1024
1536
2048
300
600
900
1200
Occ. subcarriers
Resource mapping
Duplex methods
Modulation schemes
Coding schemes
Multi-antenna support
72
84
180
192
Distributed or contiguous
FDD and TDD
QPSK, 16-QAM, 64-QAM, adaptive
1/3 rate ”tail-biting convolutional code”
1/3 rate Turbo code
Yes
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Resource mapping for E-UTRA
•
Time-frequency resources are organised in ”Resource blocks”
spanning 12 SC x 7 symbol intervals (180 kHz x 0.5 ms)
•
Diversity permutation is by mapping ”virtual resource blocks” to
”physical resource blocks”
•
Uplink is always localized mapping using SC-FDMA
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E-UTRA frame structures
One downlink slot T slot
Frame structure type 1 (FDD)
DL
N symb
One radio frame, Tf = 307200Ts = 10 ms
OFDM symbols
Resource block
Resource
resource elements
block
DL
#0
#1
#2
#3
#18
#19
RB
subcarriers
N symb  N sc
One subframe
N sc
RB
Resource element ( k , l )
Resource
element:
One time-frequency symbol
DL
N RB  N sc
RB
subcarriers
Frequency
One slot, Tslot = 15360Ts = 0.5 ms
Slot: 0.5 ms
CP0
Symb#0
CP1
Symb#1
CP2
Symb#2
CP3
Symb#3
CP4
Symb#4
Time
l 0
DL
l  N symb  1
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CP5
Symb#5
CP6
Symb#6
Multi-antenna support
•
Beamforming
–
•
Space-Time Coding (STC)
–
•
”Baseline” configuration: 2x2 (DL)
1x2 (UL)
Mobile WiMAX
–
•
Higher peak rates and increased throughput. Multiple streams are transmitted over
multiple antennas. The receiver must also have multiple antennas to separate the
different streams.
E-UTRA
–
•
Transmit diversity such as Alamouti coding to provide spatial diversity and reduce
fading margin
Spatial Multiplexing (SM) - MIMO
–
•
Multiple antennas are used to transmit or receive weighted signals to improve
coverage and capacity
Minimum requirements, Wave II: 2x2 (DL), 1x2 (UL)
Reference signal (pilot) positions
identify the different Tx antennas
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E-UTRA vs. Mobile WiMAX
•
Sub-carrier distance and useful
symbol time
–
•
•
Cyclic prefix/guard interval
–
Mobile WiMAX more robust to multipath
delays
–
Extended CP of E-UTRA an option for long
delays
Basically same
Df = 15 kHz
TU = 66.67 ms
Similar
Mobile WiMAX
No clear winner when it comes to
performance on the physical layer
Df = 10.94 kHz
•
TCP  5 ms
Complexity
–
•
E-UTRA
Bandwidth support
–
•
E-UTRA more robust to Doppler
Migration and co-existence
–
TCP = 11.4 ms
Frequency
TU = 91.4 ms
Time
E-UTRA is taylored to ease co-existence
with and migration from WCDMA/HSPA
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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, hierarchical
modulation
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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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Digital Terrestrial Broadcast, DVB-T/-H
•
Broadcast technologies using OFDM
–
No multiple access!
•
Channel bandwidths: 5, 6, 7, 8 MHz
•
Number of subcarriers (incl pilots):
•
–
2K mode: 1705 (2048),
–
4K mode: 3409 (4096) - only DVB-H
–
8K mode: 6817 (8192)
Subcarrier spacing (8 MHz channel):
–
•
Useful symbol length:
–
•
224 ms, 448 ms, 896 ms
Guard interval (Cyclic prefix):
–
•
4.464 kHz, 2.232 kHz, 1.116 kHz
1/32, 1/16, 1/8, 1/4 of useful symbol length:
Modulation: QPSK, 16-QAM, 64-QAM,
hierarchical modulation
1/32
1/16
1/8
1/4
2K
7 ms
14 ms
28 ms
56 ms
4K
14 ms
28 ms
56 ms
112 ms
8K
28 ms
56 ms
112 ms
224 ms
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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 wireless
standards
– Fixed and nomadic wireless broadband: Wi-Fi, Fixed WiMAX
– Digitial terrestrial broadcast: DVB-T, DVB-H
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