1 Tor K Moseng, Handoff in Wireless Internet Access Trial Lecture Vertical and Horizontal Handoff in...

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Tor K Moseng, Handoff in Wireless Internet Access

Trial Lecture

Vertical and Horizontal Handoff in Wireless Internet Access

Tor K Moseng

Centre for Quantifiable Quality of Service in Communication Networks

Dept. of Telematics, NTNU

19.06.09

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Outline

• Introduction

• Horizontal Handover– Handover in GSM

– Handover in WiFi

• Vertical Handover– Handover UMTS-WiFi

• Handover Approaches

• Standards– IEEE 802.21

– UMA

– CALM

• Visions

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Wireless Internet Access

• Different wireless networks available– E.g. GSM/GPRS, UMTS, WiFi, WiMAX

• Mobility is Essential– Changes the users’ behavior

– Internet access from any wireless device

• Always best connected– Multi-mode equipment

Introduction

Internet

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Wireless Internet Access

• What is handover?– Changing the point of connection while communicating

• Why is handover needed?– Mobility

– User preferences

• What is the objective?– Handover procedure without a users notice

Seamless handover

Introduction

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Network Coverage

Introduction

WPAN WLAN WMAN WWAN Satellite

BluetoothRFID

WiFiIEEE 802.11

WiMAXIEEE 802.16

GSM/GPRSUMTS

GPSGALILEO

Wireless Personal Area Network – In a person’s proximityWireless Local Area Network – Home, Hotel, AirportWireless Metropolitan Area Network – City wideWireless Wide Area Network – Regional, Cellular systemsSatellite – Worldwide coverage

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Introduction – Use Case 1BSC

BS1 BS2 BS3

1. Connect to BS1 and start conversation2. Moving out of BS1’s coverage – connect to BS23. Moving out of BS2’s coverage – connect to BS34. Conversation ended – still within BS3’s coverage

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Introduction – Use Case 2

Ethernet

WiFi

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

1. Wired connection at the working desk2. Moving indoor3. Moving outdoor4. Moving into a hot-spot

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Horizontal Handover

• Horizontal handover is when a mobile terminal changes its point of connection within the same type of network– E.g. from a cell to another in GSM

– E.g. from an access point to another in WiFi

• Reasons for handover

– Worse signal quality or loss of signal

– Traffic load balancing

– Cost

Horizontal Handover

BSC

BS1 BS2 BS3

BSC

BS1 BS2 BS3

BSC

BS1 BS2 BS3

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Handover in GSM

• Network-controlled, mobile terminal assisted handover– The network takes the handover decisions

– The mobile terminal supervises and reports its signal quality

• Three types of handover– Intra-BSC handover

– Inter-BSC handover

– Inter-MSC handover

Horizontal Handover

BSCBSC BSC

MSC

MSC

BSC

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Handover in WiFi

• Mobile terminal-controlled, network assisted handover– The mobile node chooses new AP to re-associate with

– The network exchanges information after re-association

• Handover in four parts

Horizontal Handover

Distribution System

AP1 AP2

BSS1 BSS2

IAPP (IEEE 802.11f)

1a. Probe request1b. Probe response2. Authentication3. Re-association4. Connection handover






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Vertical Handover

• Vertical handover is when a mobile terminal changes its point of connection in a different type of network– E.g. from a wired Ethernet connection to an access point in WiFi

– E.g. from an access point in WiFi to a cell in UMTS

• Reasons for handover– Worse signal quality or loss of signal

– Performance requirements (e.g. bandwidth)

– Cost

– Power consumption

Vertical Handover

Ethernet

WiFi

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

Ethernet

WiFi

UMTS

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Challenges in Vertical Handover

• Multi-mode devices

• Power consumption

• QoS– Available capacity

– Security

• Timing

• The business model

• Session continuity

Vertical Handover

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Handover UMTS-WiFi

1. Open coupling– No common subscriber database and billing

– Poor handover performance

2. Loose coupling– Common subscriber database and billing

– Improved handover performance

3. Tight coupling– UMTS core network interface must be supported single operator

– Improved handover performance

Vertical Handover

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Handover UMTS-WiFi

Vertical Handover

Internet

UMTSCore Network

WiFi GatewayRNC

1. Open coupling2. Loose coupling3. Tight coupling



AAA

Node B

Node B

Node BAP AP AP

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Handover Approaches

• Handover objective is a seamless handover– Smooth handover: low loss

– Fast handover: low delay Smooth and fast handover gives a seamless handover

• Lower layers handover– Hard handover

– Soft handover

• Network layer mobility– Mobile IP

Handover Approaches

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”break before make”


Hard Handover

• Old connection is broken before a new connection is activated

• Primarily used in FDMA and TDMA systems (e.g. GSM)– Different frequency ranges used in adjacent cells to minimize the interference

• When to perform hard handover?– E.g. based on measurements of the signal quality– Different schemes to avoid unnecessary handovers

Handover Approaches

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”make before break”


Soft Handover

• New connection is activated before the old is broken

• Used in UMTS to improve the signal quality– Uplink and downlink signals may be combined for better signal– A mobile may in UMTS spend a large part of the connection time in soft handover– Better connection reliability

• More seamless handover

Handover Approaches

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Mobile IP

• Changing the point of connection may change the IP-address– Disrupting the on-going session

• Mobile IP is a network-layer mobility management solution– Hides the mobile node’s movement from its corresponding node

• Two IP-addresses involved– Home Address: the point of contact for corresponding nodes– Care-of-Address: the current point of connection

• Two agents involved– Home Agent: acts as a proxy and forwards packets to the CoA– Foreign Agent: allows mobile nodes to register in ”foreign” subnets

Handover Approaches

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Mobile IP

Handover Approaches

1. Session with Home Network

2. Move to a Foreign Network

3. Register its presence and Care-of-address

4. Session with Foreign Network

Home Agent

Foreign Agent

Home Address

Home Network

Foreign Network

Care-of-Address

Corresponding Node

Home Address Care-of-Address

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Standards for vertical handover

• IEEE 802.21

• Unlicensed Mobile Access (UMA)

• Continous Air-Interface for Long and Medium range (CALM)

Standards

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IEEE 802.21

• Support seamless vertical handover– Media Independent Handover (IEEE Std 802.21-2008, January 2009)– Assess on-going work related to handover in IEEE, IETF and 3GPP– GSM/GPRS, UMTS, IEEE 802.3/11/15.3/16/20

• Goals– Framework for vertical handover– Different vendors, operators and users

• Not covered– Handover policy– Security What about the business model?

Standards – IEEE 802.21

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Unlicensed Mobile Access (UMA)

• 3GPP standard for cellular systems and unlicensed wireless networks handover– A mobile centric version of IEEE 802.21

• The UMA Network Controller (UNC)– Provides an interface into mobile operators core network

– Secure transport of mobile signaling over IP

• Extends a mobile operator’s services over IP-based access networks– Use WiFi to improve coverage and performance of 3G services

Standards – UMA

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CALM

• ISO approved framework for continuous communication across various interfaces and media for vehicular users– ISO TC204/WG16 – Wide Area Communications

– IEEE 802.11/11p/15/16e/20, 2G/3G, and ITS systems

• Application support– In-vehicle Internet access

– ITS applications (focus on Vehicle Safety Communication)

– V2V communication

• Vertical handover based on IPv6 protocols (ISO 21210)

Standards – CALM

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Visions

• 4G network: Universal wireless access with much higher data rates than today

• Collection of technologies and protocols– Not just one single standard

– Seamless handover and roaming

– QoS support

• Prediction of availability is 2015 (ref:Phil Redman, Gartner)

Visions

”Anytime, Anywhere”

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Visions

• The Wireless World Research Forum (WWRF) formulates visions on strategic future research directions in the wireless field

Visions

Networks for the Wireless World must enable application- and service-independent end-to-end reachability in the global network environment.

Networks for the Wireless World should be capable to support both existing and new mobility mechanisms that enable terminals and networks to move around without being closely tied to so-called ”home” networks.

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References

• 3GPP, [Online]: www.3gpp.org• Jacques De Kegel, IBM & Wireless 2004, Presentation WIreless e-business EBO, [Online]:

http://www.ti.kviv.be/Ittelecom/EBO_overview.pdf• Knut Evensen, CALM Architecture and CALM M5 Convenor, Presentation at IEEE 802 Plenary Tutorials,

November 2006• Hussain et al., Mobility Management Challenges and Issues in 4G Heterogeneous Networks, In Proceedings of

InterSense'06, May 2006• IEEE, [Online]: www.ieee.org• IETF, [Online]: www.ietf.org• Juha Korhonen, Introduction to 3G Mobile Communications, 2nd Ed, Artech House, 2003• Lim et al., SHARE: Seamless Handover Architecture for 3G-WLAN Roaming Environment, Wireless Networks,

15:353-363, 2009• Network World, [Online]: www.networkworld.com• Charles Perkins, Presentation at an IEEE 802 Handoff Tutorial, November 2002, [Online]:

http://ieee802.org/16/tutorial/T80216-02_04.zip• Bjørn Rønning, UMTS og WLAN - konkurrerende eller komplimentære systemer, Norsk UMTS-forum, Oktober

2001, [Online]: http://www.umts.no/files/30Okt01-Bj%C3%B8rnR%C3%B8nning-%20UMTS%20forum.pdf• Sharma et al., OmniCon: A Mobile IP-based Vertical Handoff System for Wireless LAN and GPRS Links, In

Proceedings of ICPP 2004 Workshops, 2004• UMA Today, [Online]: www.umatoday.com• Wikipedia, The Free Encyclopedia, [Online]: http://en.wikipedia.org• Wireless World Research Forum, [Online]: http://www.wireless-world-research.org/• Qing-An Zeng and D.P.Agrawal, Handoff in Wireless Mobile Networks, Chapter 1, Handbook of Wireless Networks

and Mobile Computing, 2002

References

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