New and Emerging Wireless Technologies Beyond 3G

51
Lucent Technologies Bell Labs Innovations Lucent Technologies - Proprietary (RESTRICTED) L.Samuel New and Emerging Wireless Technologies Beyond 3G Sam Samuel Lucent Technologies Swindon UK

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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 Presentation

Transcript of New and Emerging Wireless Technologies Beyond 3G

Lucent Technologies

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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!!