Transcript trial_lecture

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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
Tor K Moseng, Handoff in Wireless Internet Access
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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
Tor K Moseng, Handoff in Wireless Internet Access
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Introduction
Wireless Internet Access
• Different wireless networks available
– E.g. GSM/GPRS, UMTS, WiFi, WiMAX
• Mobility is Essential
Internet
– Changes the users’ behavior
– Internet access from any wireless device
• Always best connected
– Multi-mode equipment
Tor K Moseng, Handoff in Wireless Internet Access
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Introduction
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
Tor K Moseng, Handoff in Wireless Internet Access
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Introduction
Network Coverage
WPAN
Bluetooth
RFID
WLAN
WiFi
IEEE 802.11
WMAN
WiMAX
IEEE 802.16
WWAN
GSM/GPRS
UMTS
Satellite
GPS
GALILEO
Wireless–Wide
Personal
Local
Metropolitan
Area
Area
Network
Area
Network
Network
Home,
– In–aCity
Hotel,
person’s
wide
Airport
proximity
Satellite
Worldwide
Area
Network
coverage
–– Regional,
Cellular
systems
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Introduction – Use Case 1
BSC
BS1
BS2
BS3
1.
2.
Connectout
to BS1
BS1’s
and coverage
start
BS2
3. Conversation
4.
Moving
of ended
BS2’s
– stillconversation
within
– connect
BS3’s coverage
to BS3
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Introduction – Use Case 2
UMTS
WiFi
WiFi
Ethernet
Ethernet
WiFi
UMTS
1. Moving
2.
3.
4.
Wired connection
indoor
outdoor
into
a hot-spot
at the working desk
Tor K Moseng, Handoff in Wireless Internet Access
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Horizontal Handover
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
BSC
– Worse signal quality or loss of signal
– Traffic load balancing
BS1
BS2
BS3
– Cost
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Horizontal Handover
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
MSC
BSC
MSC
BSC
BSC
Tor K Moseng, Handoff in Wireless Internet Access
10 Horizontal Handover
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
IAPP (IEEE 802.11f)
Distribution System
1a. Probe request
1b. Probe response
2. Authentication
3. Re-association
4. Connection handover
AP1
BSS1
AP2
BSS2
Tor K Moseng, Handoff in Wireless Internet Access
11 Vertical Handover
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
UMTS
WiFi
WiFi
Ethernet
Ethernet
WiFi
UMTS
Tor K Moseng, Handoff in Wireless Internet Access
12 Vertical Handover
Challenges in Vertical Handover
• Multi-mode devices
• Power consumption
• QoS
– Available capacity
– Security
• Timing
• The business model
• Session continuity
Tor K Moseng, Handoff in Wireless Internet Access
13 Vertical Handover
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
Tor K Moseng, Handoff in Wireless Internet Access
14 Vertical Handover
Handover UMTS-WiFi
Internet
1.
2.
3.
AAA
Open coupling
Loose coupling
Tight coupling
UMTS
Core Network
WiFi Gateway
RNC
Node B
Node B
AP
AP
AP
Node B
Tor K Moseng, Handoff in Wireless Internet Access
15 Handover Approaches
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
Tor K Moseng, Handoff in Wireless Internet Access
16 Handover Approaches
Hard Handover
”break before make”
• 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
Tor K Moseng, Handoff in Wireless Internet Access
17 Handover Approaches
Soft Handover
”make before break”
• 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
Tor K Moseng, Handoff in Wireless Internet Access
18 Handover Approaches
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
Tor K Moseng, Handoff in Wireless Internet Access
19 Handover Approaches
Mobile IP
Home Network
Home Agent
Home Address  Care-of-Address
Corresponding Node
Home Address
1. Session with Home Network
2. Move to a Foreign Network
Foreign Agent
Foreign Network
3. Register its presence and
Care-of-address
4. Session with Foreign Network
Care-of-Address
Tor K Moseng, Handoff in Wireless Internet Access
20 Standards
Standards for vertical handover
• IEEE 802.21
• Unlicensed Mobile Access (UMA)
• Continous Air-Interface for Long and Medium range
(CALM)
Tor K Moseng, Handoff in Wireless Internet Access
21 Standards – IEEE 802.21
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?
Tor K Moseng, Handoff in Wireless Internet Access
22 Standards – UMA
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
Tor K Moseng, Handoff in Wireless Internet Access
23 Standards – CALM
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)
Tor K Moseng, Handoff in Wireless Internet Access
24 Visions
Visions
• 4G network: Universal wireless access with much
higher data rates than today
”Anytime, Anywhere”
• 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)
Tor K Moseng, Handoff in Wireless Internet Access
25 Visions
Visions
• The Wireless World Research Forum (WWRF) formulates visions
on strategic future research directions in the wireless field
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.
Tor K Moseng, Handoff in Wireless Internet Access
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References
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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
Tor K Moseng, Handoff in Wireless Internet Access