Lucent Technologies Bell Labs Innovations 1 A Survey of Enabling Technologies for 3G+ Wireless Systems Vincent Lau Bell Labs, Lucent Technologies Dec 20,

Lucent TechnologiesBell Labs Innovations1

A Survey of Enabling Technologies for 3G+ Wireless Systems

Vincent LauVincent Lau

Bell Labs, Lucent TechnologiesBell Labs, Lucent Technologies

Dec 20, 2002Dec 20, 2002

4G???


Outline Background on Cellular SystemsBackground on Cellular Systems

Evolution of Cellular SystemsEvolution of Cellular Systems

Advanced Technologies for 3G+ SystemsAdvanced Technologies for 3G+ Systems– Physical Layer Enhancement:Physical Layer Enhancement:

» Multiple Antenna Processing - BLASTMultiple Antenna Processing - BLAST» OFDMOFDM» Utilization of FeedbackUtilization of Feedback

– MAC Layer Enhancement:MAC Layer Enhancement:» Adaptive SchedulingAdaptive Scheduling

– Architectural Enhancement:Architectural Enhancement:» Information Hot-spot ArchitectureInformation Hot-spot Architecture

Illustration with UMTS - HSDPA:Illustration with UMTS - HSDPA:


Background of Cellular Systems Key Components:Key Components:

– Mobile station, base station, switch.Mobile station, base station, switch.– Bottleneck is usually on the air interface due to the limitation on Bottleneck is usually on the air interface due to the limitation on

radio resource.radio resource. Radio Resource:Radio Resource:

– Power, BandwidthPower, Bandwidth


Evolution of Cellular Systems

1G systems (AMPS, TACS)1G systems (AMPS, TACS)– Analog Transmission (FM). Analog Transmission (FM). – Voice Applications only.Voice Applications only.

2G systems. (GSM, CDMA, IS54)2G systems. (GSM, CDMA, IS54)– Digital Transmission.Digital Transmission.– Voice and Data applications (Circuit Switched only).Voice and Data applications (Circuit Switched only).– Cellular and PCS. Cellular and PCS.

2.5G systems (GPRS/EDGE, 3G1X).2.5G systems (GPRS/EDGE, 3G1X).– Digital Transmission,Digital Transmission,– Circuit Switched voice and data (same as 2G + medium speed)Circuit Switched voice and data (same as 2G + medium speed)– Packet switched data (medium speed, No QoS).Packet switched data (medium speed, No QoS).– Overlay Infrastructure with 2G Systems.Overlay Infrastructure with 2G Systems.


GPRS Infrastructure

Voice Path - same Voice Path - same infrastructure as GSM.infrastructure as GSM.

Data Path - via an Data Path - via an overlay IP-based overlay IP-based network of SGSN - network of SGSN - GGSN. GGSN.


Evolution of Cellular Systems 3G systems.3G systems.

– Digital transmission,Digital transmission,– Circuit switched voice and data (low speed)Circuit switched voice and data (low speed)– Packet switched data services (high speed ~ 2Mbps, with QoS).Packet switched data services (high speed ~ 2Mbps, with QoS).– Integrated Core Network Infrastructure between voice and data Integrated Core Network Infrastructure between voice and data

paths.paths.


Post 3G Systems

3G+ Systems??3G+ Systems?? – Based on existing 3G Based on existing 3G

spectrum (not new spectrum (not new spectrum).spectrum).

– By 2010, 66% of the By 2010, 66% of the revenues will come revenues will come from data services from data services

– UMTS - Release 99/4 UMTS - Release 99/4 systems alone will not systems alone will not be capable to meet be capable to meet these demands. these demands. (Realistic outdoor data (Realistic outdoor data rates will be limited to rates will be limited to 384kbps).384kbps).

– Ultra high speed packet Ultra high speed packet data service (10.8 data service (10.8 Mbps)Mbps)

– All-IP Core Network.All-IP Core Network.


Advanced Technologies – Physical Layer Enhancement

– Multiple Antenna (MIMO) Processing:Multiple Antenna (MIMO) Processing:» Traditionally, the speed of a wireless link is limited by the Traditionally, the speed of a wireless link is limited by the

radio resource (power, bandwidth).radio resource (power, bandwidth).» When the transmitter has antennas and the receiver When the transmitter has antennas and the receiver

has antennas, the link speed increases linearly with has antennas, the link speed increases linearly with given the same power and given the same power and

bandwidth budget.bandwidth budget.» Multiple Antenna introduces Multiple Antenna introduces Spatial DimensionSpatial Dimension into the into the

radio resource set. radio resource set. » Similar to fixed line scenario except there are mutual Similar to fixed line scenario except there are mutual

interference between the spatial channels.interference between the spatial channels.

min ,T Rn n

TnRn


Advanced Technologies – Physical Layer Enhancement BLAST (Bell-Labs Layered Space-Time Architecture)BLAST (Bell-Labs Layered Space-Time Architecture)

– At the transmitter, n independent data streams are At the transmitter, n independent data streams are transmitted out of the n antennas on the same bandwidth. transmitted out of the n antennas on the same bandwidth.

– At the receiver, each receive antenna "sees" all of the At the receiver, each receive antenna "sees" all of the transmitted sub-streams superimposed, not separately.transmitted sub-streams superimposed, not separately.

– If multipath scattering is sufficient, these n data streams If multipath scattering is sufficient, these n data streams have different have different spatial signaturesspatial signatures to each of the n receive to each of the n receive antennas and they are separable. antennas and they are separable.

– The processing involved is linear and could be (interference The processing involved is linear and could be (interference nulling or MMSE).nulling or MMSE).

– Lucent has produced the world’s first BLAST receiver chip Lucent has produced the world’s first BLAST receiver chip for mobile device.for mobile device.

–


Advanced Technologies – Physical Layer Enhancement Block DiagramBlock Diagram


Advanced Technologies – Physical Layer Enhancement Orthogonal Frequency Division Modulation (OFDM)Orthogonal Frequency Division Modulation (OFDM)

– Traditionally, transmission of a wideband signal is more Traditionally, transmission of a wideband signal is more difficult than a narrowband signal.difficult than a narrowband signal.

– This is due to multi-path effects This is due to multi-path effects Inter-symbol interference. Inter-symbol interference.– Complex equalizer is needed to overcome this effect. Complex equalizer is needed to overcome this effect. – OFDM is an effective technique to transmit wideband signal.OFDM is an effective technique to transmit wideband signal.– Serial input data is split into N parallel streams, each stream Serial input data is split into N parallel streams, each stream

is fed into a “frequency channel”. is fed into a “frequency channel”. – With respect to each data stream, it is a narrowband signal, With respect to each data stream, it is a narrowband signal,

and could get through the channel easily without equalizer.and could get through the channel easily without equalizer.– At the receiver, the N parallel streams are combined. At the receiver, the N parallel streams are combined.


Advanced Technologies – Physical Layer Enhancement Utilization of Feedback:Utilization of Feedback:

– Wireless channel is time varying. {Good Wireless channel is time varying. {Good Bad} Bad}– Adaptive transmission is possible to exploit the time varying Adaptive transmission is possible to exploit the time varying

nature of the channel.nature of the channel.– High throughput transmission mode is employed when High throughput transmission mode is employed when

channel is good, channel is good, – When channel is bad, low throughput transmission mode is When channel is bad, low throughput transmission mode is

employed for better protection. employed for better protection. – Need the feedback of channel condition to the transmitter.Need the feedback of channel condition to the transmitter.


Advanced Technologies – MAC Layer Enhancement

Jointly Adaptive MAC Scheduling:Jointly Adaptive MAC Scheduling:– For voice service, data source is quite steady. Optimal strategy For voice service, data source is quite steady. Optimal strategy

is to power control users so as to act against fading is to power control users so as to act against fading maintain maintain a steady channel throughput.a steady channel throughput.

– For packet data service, data source is in burst. Optimal For packet data service, data source is in burst. Optimal strategy is to act in line with fading. Increase power when strategy is to act in line with fading. Increase power when channel is good. Decrease power when channel is bad. channel is good. Decrease power when channel is bad.

– For multi-user network, MAC layer is used to coordinate For multi-user network, MAC layer is used to coordinate resource allocation among different users.resource allocation among different users.

– Between a user and a base station, the link throughput (speed) Between a user and a base station, the link throughput (speed) is adaptive based on the link condition. is adaptive based on the link condition.

– The key is to have a The key is to have a jointly adaptive MAC layer and physical jointly adaptive MAC layer and physical layerlayer. .

– Priority is given to users with good channel conditions. (because Priority is given to users with good channel conditions. (because they could use the radio resource more effectively). they could use the radio resource more effectively).


Advanced Technologies – MAC Layer Enhancement

Since users are independent Since users are independent with each other, we could with each other, we could always find users with good always find users with good channel condition at any channel condition at any given time (if the total given time (if the total number of user is large) number of user is large) Multiuser Diversity. Multiuser Diversity.

In addition to maximum In addition to maximum network capacity, fairness is network capacity, fairness is also an important attribute.also an important attribute.


Advanced Technologies – MAC layer Enhancement

Proportional fair is another common objective of scheduling. Proportional fair is another common objective of scheduling.

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000Kbps

%U

Es

with

PC

T <

ab

scis

sa

Proportional Fair

Normalized Max C/I

Max C/I


Advanced Technologies – Architectural Enhancement Information Hot-spot Architecture (Wireless LAN vs Cellular Systems):Information Hot-spot Architecture (Wireless LAN vs Cellular Systems):

– High speed, low mobility, localized-coverage wireless multimedia High speed, low mobility, localized-coverage wireless multimedia access --> hot spot access points. (e.g. Wireless LAN Access access --> hot spot access points. (e.g. Wireless LAN Access Point).Point).

– Medium speed, high mobility, macro-coverage --> cellular wireless. Medium speed, high mobility, macro-coverage --> cellular wireless. (e.g UMTS)(e.g UMTS)

– Mobility between localized hot-spots and cellular wireless through Mobility between localized hot-spots and cellular wireless through mobile-IP. mobile-IP.

The WLAN advantages:The WLAN advantages:– Order of magnitude higher data rates than 3GOrder of magnitude higher data rates than 3G– Rapidly falling price (available from retail)Rapidly falling price (available from retail)– HW embedded in laptops (Dell, IBM, Toshiba, Fujitsu, Acer). HW embedded in laptops (Dell, IBM, Toshiba, Fujitsu, Acer).

SW supported in Window XPSW supported in Window XP– 50% of USA laptops and PDAs are expected to be WLAN-50% of USA laptops and PDAs are expected to be WLAN-

enabled by 2004.enabled by 2004.


Information Hot-spot Architecture (Tight Integration)

BS

3G RAN

BS

W-LANHot Spot WSP

Corporateor ISP Internet Core

Network

Local AAA

Home AAA


Information Hot-spot Architecture (Loose Integration)

BSBS

WLANHot Spot

Ethernet

Internet

3G RadioAccess Network

Home Agent

Home AAAServer

Local AAAServer

Local AAAServer

802.11b Access Points

Laptop with Mobile IP client

Foreign Agent

Link Layer Mobility Link Layer Mobility

Network Layer Mobility

HomeService Provider

Network

802.11bPCMCIA

Card

3GPCMCIA

Card

3G Core Network(Includes Foreign Agent)


Mobile-IP Operation

• Traffic is sent as usual to the home subnet

• The home agent intercepts (Proxy ARP) the traffic while the mobile node is registered as away

• Traffic is tunneled to its current location

• Traffic from the mobile node can go directly to the correspondent host

MobileNode

HomeAgent

ForeignAgent


Wireless Virtual Private Network

W-LANHot Spot

Ethernet

Internet

Xedia AP1000

HA

CorporateNetwork

NavisRadiusHome AAA Server

802.11 Access Points

Dual-mode terminal w/MobileIP client

Xedia FA

NavisRadiusLocal AAA

Server

Mobile-IPtunnel

Lucent PCF

BS

BSC

BS

PDSNSpringtide

(FA)

WSP

NavisRadiusLocal AAA

Server

End-to-endIPSec tunnel


An Example of 3G+ Evolution - UMTS HSDPA (High Speed Downlink Packet Access)

Release 99/4

DCH/DSCHDCH/DSCH

2 Mbps Packet

Mar 00

Dec 00

R99

R4

Hybrid ARQHybrid ARQ Dynamic Scheduling

Dynamic Scheduling

Adaptive Modulation & Coding

Adaptive Modulation & Coding

HSDPA Release 5

EnhancedChannel Structure

EnhancedChannel Structure

2.4Mbps Packet

June 02

HS-DSCH

‘03

Fast Cell Selection

Fast Cell Selection

MIMOMIMO

HSDPA Release 6

10.8 Mbps Packet (2x2)20 Mbps Packet (4x4)

HS-DSCH


Practical considerations at the terminal

For uncorrelated fading, 1/2 lambda spacing is sufficient For uncorrelated fading, 1/2 lambda spacing is sufficient because of local scatterers. because of local scatterers.

Each antenna requires RF/IF chain. Significant cost savings Each antenna requires RF/IF chain. Significant cost savings using direct conversion (homodyne) solutions.using direct conversion (homodyne) solutions.

20% and 70% of baseband processing used by VBLAST 20% and 70% of baseband processing used by VBLAST detector and turbo decoder, respectively, for (4,4) receiver. detector and turbo decoder, respectively, for (4,4) receiver. Overall processing is within range of existing hardware Overall processing is within range of existing hardware technologies. technologies.

13cm

15cm

Antennas used in MIMO channel measurements

Documents

Lucent Technologies Bell Labs Innovations 1 A Survey of Enabling Technologies for 3G+ Wireless Systems Vincent Lau Bell Labs, Lucent Technologies Dec 20,