Advanced Topics in Next-Generation Wireless Networks

Advanced Topics in Next-Generation Wireless Networks

Qian ZhangDepartment of Computer Science

HKUST

Introduction of Wireless Networks

Why Wireless?

• Convenience and flexible

• Mobility

• Coverage

• Easy to deploy

• Low cost

• New applications potential

• Improved quality of life (people with disabilities)

anytime

anywhere

any device

service

4A: Anytime, Anywhere, Any device, and Any service

Fast Growing Devices Create New Connectivity Demands

Wireless Technologies

WWAN (3G,4G?)

WLAN (Wi-Fi)

WPAN

WMAN (Wi-Max)

BluetoothUWBRFID

coverage

Big Picture – WPAN’s

• WPAN technologies – RFID, Bluetooth, UWB• RFID used in tagging applications, restricted

environments (supermarkets, institutions)• 10 billion RFID tags been sold by the end of 2005

(source: Deloitte & Touche)

• Bluetooth – technology has matured • 56% of mainstream devices commercialised will

have Bluetooth support by 2008 (Source: IDC)

• UWB: bandwidth larger than 500MHz• Two main camp: DS-UWB (Motolora) vs. MBOA-

OFDM UWB (Intel+TI)

laptops

MobileCluster

cameraspocketPC

CECluster

HDTV

STBs

VCRs

PVRs

audio

systems

tablets

printers

speakers

MP3

PDA

PCCluster

camcorders

ConsoleGames

CordlessPhones

3GHandsets

storagedevices

Scanners

Projector

Ultra WideBand (UWB)

WLAN (WiFi-802.11x)

802.11n100 Mbps (above MAC)

802.11a

802.11g 802.11b

54 Mbps5 GHz

11 Mbps

2.4 GHz

54 Mbps

2.4 GHz

802.11e

Quality of Service

1999 2001 2003 2005 2007

802.11i

Enhanced Security

802.11k

Radio Resource Measurement

Physical Layer Enhancements

IEEE 802.16dIEEE 802.16dAir I/F Fixed BWAAir I/F Fixed BWA

Approved 07/04Approval 05/05 Corrigenda (TGh)

WiMAX 1st certificate 07/05

Chipset for Indoor-outdoor CPE

• Intel is the main driver for WIMAX: Integration in Centrino is the disruptive goal

IEEE 802.16eIEEE 802.16eAir I/F Fixed Air I/F Fixed & Mobile BWA& Mobile BWA

Approval 07/05

Chipset for PCMCIA No handover

Chipset for Centrino Handset

Approval 05/06 Corrigenda (TGh)

Possible delay

200620062005200520042004 2008 2008 20072007

Big Picture –WMAN’s

WiMax (Worldwide Interoperability for Microwave Access)

•Standard & Chipset Availability

Business, SME, SOHO Access Business, SME, SOHO Access

Residential FixedResidential Fixed WDSL BB AccessWDSL BB Access

Nomadic PCNomadic PC

WiFiWiFi

WiFi-Hotspot WiFi-Hotspot FeedingFeeding

Mobile Mobile PC/PADPC/PAD

NB orBTS

2G/3G 2G/3G FeedingFeeding

Hot ZonesHot ZonesCampu

s Airport

WiMAX

Base Station

IEEE 802.16-2004IEEE 802.16-2004

WiMAX Applications in 2005

Fixed Services



WiFiWiFi


Mobile Mobile PC/PADPC/PAD

Nomadic PCNomadic PC

NB orBTS



s Airport

WiMAX

Base Station

IEEE 802.16-2004IEEE 802.16-2004& IEEE 802.16e& IEEE 802.16e

WiMAX Applications in 2006-2007

Nomadicity, Solutions for Laptops (PCMCIA)



WiFiWiFi


NB orBTS



s Airport

Portable PCPortable PC

Mobile Mobile PC/PADPC/PADWiMAX

Base Station

IEEE 802.16eIEEE 802.16e

WiMAX Applications in 2007-2008

Fully Mobile, Integrated Solutions in Laptops and PAD

IP Network

WCDMA5MHz2Mbps

HSDPA5MHz

10Mbps

CDMA20001xEV-DV1.25MHz5Mbps

MBWA (802.20)OFDM-5MHz (<3.5GHz)

5Mbps (250kmph)

WLAN (802.11)20MHz

54Mbps

UWB (802.15.3a)7.5GHz (3.1-10.6GHz)

480+Mbps

HarmonizedAll IP CN

WMAN (802.16e)OFDM-5MHz (2-6GHz)

15Mbps (60kmph)

Services/Applications

Services/Applications

TD-SCDMA5MHz2Mbps

WWAN (3G and Beyond)

Overlay Networks- the Global Goal

Integration of heterogeneous fixed andmobile networks with varyingtransmission characteristics

verticalhand-over

horizontalhand-over

campus-based

metropolitan area

regional

in-house

Wireless Networks vs. Fixed Networks

• Restrictive regulations of frequencies– Frequencies have to be coordinated, useful frequencies

are almost all occupied

• Low transmission rates– Local 11~54 Mbit/s, regional currently, e.g., ~40 kbit/s

with GPRS/CDMA

• Higher loss-rates due to interference– Emissions of, e.g., engines, lightning

• Higher delays, higher jitter– Connection setup time with several hundred

milliseconds for some wireless systems

Wireless Networks vs. Fixed Networks (Cont.)

• Lower security, simpler active attacking– Radio interface accessible for everyone, base

station can be simulated, thus attracting calls from mobile phones

• Always shared medium– Secure access mechanisms important

• Close and complex inter-layer interaction

Influence of Wireless Communication to the Layered Model

– service location– new applications, multimedia– adaptive applications– congestion and flow control– quality of service– addressing, routing,

device location– hand-over– authentication– media access– multiplexing– media access control– encryption– frequency– modulation– interference– attenuation

• Application layer

• Transport layer

• Network layer

• Data link layer

• Physical layer

OSI or TCP /IP stack MAY NOT be the way to go!

Current Trend : Eliminate layers or introduce hooks such that layers can interact with each other

Classification of Wireless Networks

• Cellular Networks– Organized, base stations that are regularly placed.

Mobiles communicate only with base stations

• Wireless LANs– Less organized; access points with which mobile nodes

communicate

• Ad hoc/Multi-hop networks– No infrastructure; nodes potentially move and network

dynamically changes

• Sensor Networks– application specific; mobility is limited (perhaps to

selected subset of nodes); tiny nodes that are resource and energy constrained

Ad Hoc Network Characteristics

• Peer-to-peer• Multihop• Dynamic• Low power

• Zero-administration• Auto-configured • Autonomous• Really “anytime, anywhere”

Wireless Mesh Networks

Key Players:

MotorolaNortelMicrosoftIntel (802.11s)MeshdynamicsFiretideStrixBellair….

Most the relay nodes are assumed to be static

Possible Applications for Multi-Hop Networks

• Emergency response

• Military communications

• Broadband Internet access sharing

• WLAN coverage extension

• Home and conference networks

• Community networks

The Spectrum Problem

Spectrum Dilemma: We are not running out of spectrum; we simply aren’t using it properly!

All Spectrum May Be Assigned, But … Most Spectrum is Unused

Overview of Open Spectrum

• Primary devices – Utilize assigned spectrum when

desired– Movement and channel utilization

varies over time

• Secondary devices– Seek to utilize remaining “available

channels” without interfering primary users

• Find optimal balance between maximizing spectrum utilization and minimizing harmful interference

Open spectrum enables opportunistic spectrum access to provide 10x Improvement by reusing wasted spectrum

channelsRequirement: cognitive radios

What is a Cognitive Radio?

• Wireless communication radios e.g., 802.11 a/b/g/n, can be described as fixed and adaptive – A fixed radio has its technical characteristics set at the time of

manufacturing– An adaptive radio can respond to channel conditions that

represent one of a finite set of anticipated events

• Cognitive radios– It can dynamically take advantage of spectrum– It provides spectral awareness in support of FCC initiatives in

spectral reuse– Can respond intelligently to an unanticipated event, i.e., a

channel that it has never encountered before – It can take decisions based on many trained observations

Trends – Industry

• Two distinct markets evolve with different technologies and paradigms

Wide area wireless Local access wireless

•Seamless mobility•High speeds•Any-time anywhere•Moderate data rates

•”Cordless” access•Stationary use•High data rates

Trends – Technology

• Increasingly complex and heterogeneous network environment– Many different types of networks, from simple to

complex, operated by different types of operators– Many different access technologies - but several of

those developed today will not survive– More “niche” wireless standards – no single “4G”

radio standard

• Gradually shift towards multi-standard “Ambient Networks”

Wide Area Ambient Networks

Public UMTSNetworks

Public GPRS

Networks

Home

Office

WLAN

WLAN & UWB

WMAN (WiMAX)

WPAN (BT)

End-to-end Reconfigurability for Seamless Experience

Fixed

WLAN

WiMAX

2.5/3G

4G

UWBDVB

DAB

Other Access

Networks

Ubiquitous Access

Pervasive Service

DynamicResource Management

Different administrative domains

All-IP infrastructure

Heterogeneous Systems

Heterogeneous Environments and Contexts

Heterogeneous Devices

Move Forward: Cognitive Networking and System

Automatic Environment

Understanding and Dynamic

Spectrum Utilization

Sense/Aware

Adapt

LearningMistake Correcting

Autonomy

Documents

Advanced Topics in Next-Generation Wireless Networks