new and emerging wireless technologies beyond 3g
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New and Emerging Wireless Technologies Beyond 3G. Sam Samuel Lucent Technologies Swindon UK. TOC. Economics and Vision Background to the Problem Future and Emerging Technologies MIMO OFDM Beam forming – IA and Antenna Array Interference cancellation Network Time Scheduling - PowerPoint PPT PresentationTRANSCRIPT
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New and Emerging Wireless Technologies Beyond 3G
Sam Samuel
Lucent Technologies
Swindon UK
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TOC
• Economics and Vision• Background to the Problem• Future and Emerging Technologies
– MIMO – OFDM– Beam forming – IA and Antenna Array– Interference cancellation – Network Time Scheduling
• IEEE Approaches• Summary
3
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Wireless Experience Curve: 1985 to 1996
Note: Cost excludes marketing and sales expense and are in 1996 dollars
$0.1
$1
$10
1 10 100 1000 10000
Co
st p
er M
inu
te
Cumulative Minutes (B)
19961995
199419931992
19911990
19891988
19871986
1985
CEO’sReal Estate Agents
Replace Calling Cards
Intercom
Source: G.Blonder, AT&T Labs, 1977
Note: DRAM and airtime both reduced ~10x from 1985-1995
Elasticity ~ 3
•Next generation systems must be spectrally efficient across the network (bandwidth where needed).
•Equipment providers will provide the “compilers” for application creation.
•Partnering will be the norm.
Def of Elasticity: %change in X/% change in y
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Economics and Visions
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Ambient Control Space
PAN
Personal
VAN
Vehicular
HAN
Home
CAN
Community
Ambient Connectivity
2.5 G2.5 G
FixedFixed3G3G
WLANWLAN4G4GCorporateCorporate
Ambient Networks:- Common Control Services- Dynamic Network Composition
ServicesServices ServicesServices
Information Anywhere Vision:Example project – EU 6FP Ambient Networks
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Background to the problem Motivation
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The wireless channel
Pre
ceiv
ed
delay spread
i
iii ttjath )()exp()(
•Scattering causes local signal fading
•Delay spread dependent on environment (small for indoor, large for macrocell)
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Channel Normal-modesP
r
delay spread
i
iii ttjath )()exp()(
t
Pr
f
• Classic static multipath channel is linear.• Normal modes are simple sinusoids. OFDM then is optimal in this sense.• Information is broken into small frequency bands with flat fading. Great for
MIMO type applications.• Active research areas within Bell Labs:
– OFDM, chirped pulses, MC-CDMA, OFDM-CDMA for legacy and practical implementation
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Increasing the Data Rate in CDMA
Rake ReceiverOriginal signal Multipath channel Rx signal
bandwidth
bit
rate
bit rate goes to zero at infinite bandwidthand fixed power
multiple access noise floorideal
time diversity
UMTS
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0
400
800
1200
1600
5 10 15 20 25
Pac
ket
Siz
e
Netscape Browser access to www.adobe.com:• blue dots are downlink packets, red dots are uplink packets.• average downlink Kbps to 1 second peak = 4.3:1• average uplink Kbps to 1 second peak = 4.7:1• MRU was 1500 bytes• TCP Window Size was 8,192 bytes
Live Wireless Transaction Measurements
Traffic characteristics:• Initial download of HTTP skeleton resulted in GET of large objects. Many 1500 packets retrieved.• Period 9 - 20 consumed by DNS accesses to resolve www.xxx.com addresses to IP addresses.• End of transaction resulted in many small object retrievals. Large uplink payloads for smaller downlink payloads.• Latency chart illustrates queuing within system as generated load piles up in uplink and downlink directions.• This traffic profile is typical of Web accesses.
5 10 20 25
Lat
ency
sec
We cannot ignore delay – TTI Issues
We cannot ignore uplink – Symmetry Issues
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0
50
100
150
200
250
300
350
0 100 200 300 400 500
Usable Channel Rate (Kbps)
TC
P t
hro
ug
hp
ut
(Kb
ps)
l=400 ms
l=50 msThroughput = 8KB/(lat + 8kb/ucr)
0
50
100
150
200
250
300
350
0 100 200 300 400 500
Usable Channel Rate (Kbps)
TC
P t
hro
ug
hp
ut
(Kb
ps)
l=400 ms
l=50 msThroughput = 8KB/(lat + 8kb/ucr)
General Throughput Equation
• To optimize data performance we should combine rate and power control
• OFDM is convenient for water filling• Keep number of sub-carriers manageable for uplink
channel information
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Future and Emerging Technologies
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MIMO
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Space: The Last Frontier
Convergence of ubiquitous wireless access and broadband internet creates insatiable demand for high bit rate wireless access
System capacity is interference limited - cannot be increased by increasing transmitted power
The spectrum has become a scarce and very expensive resource
For Cellular systems reducing cell size is not viable
Increasing spectral efficiency with multiple transmit and multiple receive antennas opens a new dimension, space, offering exceedingly high bit rates without increasing transmitted power bandwidth allocation
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Bandwidth Efficiency Limits
Tx Rx
C. Shannon Bell Labs Technical Journal, 1950
N
SC 1log2
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Efficiency Limits with a Single Array
Adding a single array does provide diversity against fading, but it does not change the (slow growth) logarithmic nature of the bandwidth efficiency limit
Tx Rx1
Rx2
RxM
...
N
SC 1log2
N
SMC 1log2
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Lifting the Limits with Dual Arrays
Tx1 Rx1s1
Tx2
TxM
...
Rx2
RxM
...
s2
sM
N
SC 1log2
N
SMC 1log2
number of antennas in the smaller of thetransmit and receive arrays
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Predicted outage capacities
SP
EC
TR
AL
EF
FIC
IEN
CY
(bp
s/H
z)
NUMBER OF UNCORRELATED ANTENNAS (M=N)
0 10 20 30 40 50 60
150
100
50
24dB18 dB 12dB
6 dB
0 dB
8
SPECTRAL EFFICIENCY vs. NUMBER ANTENNAS AT 1% OUTAGE
1N OptimumCombining at 24 dB
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0 4 8 12 160
10
20
30
40
50
Number of antennas
Cap
acity
(bi
ts)
MIMO Capacity Increases
Capacity grows as the number of antennas!
• Increases the spectral efficiency•Compact antenna arrays•Low-cost receivers
Receiver Chip(2.1mmx1.9mm)
C/W=log2(det(I+HHH))
~N*log2(1+SNR)
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MIMO
MIMO: Increase data rates by exploiting multiple antennas at both Tx and Rx.
x(1)c1 ... cK
4-QAMModulator
UserData ENC
TurboEncoder
x(2)c1 ... cK
x(3)c1 ... cK
x(4)c1 ... cK
H
Sp
ace-
Tim
eR
ece
iver
Interleave
(1)r
(2)r
(3)r
(4)r
Tx Rx
User data is encoded, modulated and transmitted
simultaneously over multiple antennas
High Data Rates
High levels of interference at the mobile requires sophisticated yet
efficient signal processing.
Channel
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The Wireless Channel in MIMO Processing
Multiple antenna techniques rely on the characteristics of the spatial signature:
• Diversity techniques rely on the assumption that distinct spatial signaturesdistinct spatial signatures correspond to different pairs of transmit-receive antennas.
• Intelligent antenna techniques rely on the efficient efficient adaptation of the array patternadaptation of the array pattern according to the spatial distribution of the desirable user and interferers.
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• Time-Switched Transmit Diversity (TSTD)
Open-Loop Transmit Diversity
• Space-Time Block Code Transmit Diversity (STC)
time
Datax1 , x2
x1
x2
time Mobile
Datax1 , x2
x1
x1*
time Mobile
time
x2
–x2*
Space-TimeBlock Code
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MIMO Research Trends
• High-performance, low-complexity receiver architectures for MIMO based on multiple iterations between a low-complexity detector and a error-correcting decoder.
• Transmitter encoding for High-Order Modulations in MIMO, allowing reduced complexity at the receiver.
• High-performance, low-complexity detection algorithms for MIMO. Algorithms based on joint-detection or serial/parallel interference cancellation techniques following space-time equalization.
Advanced MIMO receivers can be costly on the downlink due to limitations in mobile form-factor and complexity.
• Dynamic packet scheduling across multiple antennas.
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0 2 41
2
3
4
Propagation Modeling & Measurements
• narrowband channel capacity in mobile suburban 80% of theory
• narrowband channel capacity of laptop in van is 65% of theory
• Capacity improvements are real
Indoor propagation measurements consistently show high BLAST gains.Recent outdoor measurements demonstrate similar results.
120 ft
BLA
ST
/1x1
cap
acity
time (sec)
Laptop
Mobile Measurements
omni ant.
antennain laptop
theory
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OFDM
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Orthogonal Frequency Division Duplexing
• Breaks high-speed data into low-rate parallel streams• Longer symbol period reduces ISI & ICI for spread OFDM
• fn=fc+nf, where for orthogonality fTs=1
• Simple DFT implementation
cos(t)
sin(t)
IFF
T
N B
lock
f
1/NT
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Beam Forming – Intelligent Antenna
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Performance Enhancements
Transmit Diversity achieves:
• Improved call quality on the downlink by combating multipath fading.
• Reduced BTS transmit power, thereby reducing downlink inter-cell interference.
Intelligent Antennas achieve:
• Higher antenna gain - by maximising received energy or transmitting more effective power.
• Reduction of Interference by maximising Signal – to - Interference Ratio
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OmnidirectionalCell Site
Three SectorCell Site
Intelligent AntennaCell Site
• An antenna-array transceiver system.• Combined with a base station architecture and signal processing
techniques designed to dynamically select or form the “optimum”
beam pattern per user.
Intelligent Antennas
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Mobile 2
Adaptive AntennaConventional Receiver
Antenna spatial gain patterns are fixed. Adaptively “weight” and combine multiple antenna signals to optimise performance.
Mobile 1:Direct Ray
Mobile 1Mobile 1
Mobile 2:Direct Ray
Interferer
Mobile 1:Reflected Ray
Mobile 1:Reflected Ray
Mobile 1:Direct Ray
Mobile 2:Direct Ray
Interferer
Mobile 1:Reflected Ray
Mobile 1:Reflected Ray
Adaptive Antenna Principle
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Closed-Loop Transmit Diversity
• Weights are computed by the mobile as a function of the downlink channel estimates to maximise the received signal energy.
• Weights are then quantised in amplitude/phase and sent back on the uplink control channel.
Data Mobile
w
1
w
2 Feedback on Uplink
Closed-loop TxAA Quantised Weights
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Multi-Antenna Solutions
Signal fades in time and space. Include both space and time diversity
dB
Path
loss
(d
B)
antennaseparation
time
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Base and terminal Smart Antenna Prototypes
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Basestation Antenna Configurations
polarizationbeams
• two beam lobes• polarization and spacial
diversity configurations• 2-6 dB improvement• high gain for low-speed
users• 4-fold diversity on the
uplink
• 16 element tower top electronics
• 9o beamwidth with -35 dB side lobes
• Space-division multiple access
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Polarization Antennas at Mobile
Three omni-antennas co-located at feed point
Key feature to obtain MIMO gains:• achieving the separation between Antennas on the end deviceCeramic Antenna, Tripole Antenna
H
E
Without scattering polarization perpendicular to k-vectorTripole antenna
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Interference Cancellation
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Interference Mitigation (1):Cellular Downlink
Serving NodeB
(1-Antenna Tx)
K1 Codes Inter-cell Interference
K2 Codes
Multi-Antenna UE
Interfering NodeB
(1-Antenna Tx)
• Iterative detectors based on space-time filtering. Filter weights trained via transmitted pilots of the desired signal using Least squares and semi-blind (e.g. constant modulus) optimisation criteria.
Intra- and inter-cell interference mitigation algorithms at the mobile.
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Interference Mitigation (2):WLAN
• Space-time filtering at the receiver in conjunction with enhanced MAC algorithms to cope with inter-system interference.
Inter-system Interference due to co-existing technologies in unlicensed bands.
NLOS
Residential Property
802.11AP
UserTerminal
Interferer
UserTerminal
LOS
LOS
Interferer
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Interference Mitigation Advances
10 11 12 13 14 15 16 17 18 19 2010
-2
10-1
100
SNR, dB
MS
E
K=4, M=2, Nt=20, Nd=80, SIR=0dB, 500 trials
Known parameters LR with outliers selectionLS LSB SB (delta=0.1)
Conventional solutions
Proposed semi-blind solution
Finite data ML benchmark
Optimal solution:Full a priori info
Techniques advancing to point where they approaching theoretical limits
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Network Time Scheduling
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Short Delay vs. Long Delay Services
linkloss
Txpower
Delay constraints force user to power control through fades
Txpower
Schedule transmission around fades. Transmit at full power maximum rate. Higher latency.
linkloss
delay jitter
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0 20 40 60 8015
20
25
30
35
time (sec)
Tx
pow
er (
dB)
Data scheduling
Partition low and high latency services in power
low latency
high latency
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0 10 20 30 400
1
2
3
4
5
Number of users/cell
Max
imu
m T
hro
ugh
put
Inter-cell coordinationIntra-cell coordinationNo out-of-cell interference
Coordinated Cell Scheduling
• High priority packets are sent with neighbors quiet.• Coordination is local between nearest neighbour
possible 3Ximprovement
MESH Network• 802.16a • Other relay techniques being proposed in 4G research• Considered a key Future Emerging Technology by EU
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IEEE Approaches
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Impact of 802.20, 802.16 , 802.11
IEEE approach is largely OFDM based• Even IEEE 802.15.3 is OFDM based
Actively adding mobility to the standards:• 802.16e and 802.20• 802.11 considering management plane that would allow mobility
Differences:• 802.20 – wide scale mobility (vehicular)
– frequency band 500Mhz to 3.5GHz
• 802.16e – pedestrian – Based on 802.16a frequency band 2GHz to 6 GHz
Appears there is an overlap between two
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Efficiency Targets for 802.20
Source IEEE 802.20
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Peer/Peer and Client/Server Small User Population Isolated "Cells" and User Groups Non-Contiguous Coverage Indoor Operation Limited Mobility Mostly Asynchronous Traffic Slower than Ethernet
A
A
First Generation Wireless LANs
InterNet/IntraNet Ethernet-Compatible Speeds Multiple RF Bands to operate
Second-Generation Wireless LANs
A
C
BA
Larger User Population Managed Services Full Roaming/Handoff Capability Contiguous Coverage in Dense Areas Wider Area Coverage for Community LANs Mobility (Follow-Me Service) Mix of Async and Isochronous Traffic Higher System Utilization Enhanced Security
IEEE 802.11Fourth-Generation ofWireless Communications
Third-Generation Wireless Communications•TDMA•EDGE•Wideband CDMA
802.11: Indoor Wireless LAN Migration
Merge of 3G and 4G services(WLAN & WAN)
Source ATT proposal to IEEE 802.11
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Process of Managed 802.11 devices in the Standards
Inter-Access Port Protocol
Radio Resource Measurements
Remote Managed Device
(Small steps to make good progress)
Inter-Communications between APs(Now a Standard)
Ability to obtain MAC and PHY measurements by Upper Layers
(Now a Task Group)
Enable external entities to manageDevices (APs and Clients) (Proposed Next Logical Step)
Source ATT proposal to IEEE 802.11
802.11: Device Management
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IEEE impact on 4G
Mobility:Higher layer approach to mobility:• MIP and enhancements e.g. Dynamic Home Agents• Considering proposals to Link layer mobility• That all 802.xx standards adhere to MAC and VLAN bridging
Conclusion:Aim is for improved spectral efficiencyIncorporating ideas of:• PAN - 802.15.x• VAN – 802.20, 802.16e• HAN – 802.11(a-g)• CAN – 802.16a
Potential High Impact on 4G
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Summary
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In this talk we have• Looked at the motivation and vision for the
emergence of new technologies• Looked at which technologies are likely to succeed• Noticed that the IEEE approach to 4G
standardisation may succeed before others
Thank You!!