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ECE544: Communication Networks-II, Spring 2007
D. Raychaudhuri
Lecture 8
Includes tutorial materials from C. Perkins & D. Reininger
Cellular Concept of Mobility
• Users have a home system but can register at visited systems to make and receive calls – Single Number Service
• Users can roam among systems during a call and the call is handed-off without being dropped.
Functional Elements
Home System Visited System
HLR AC
VLR
AuthenticationCenter – Authenticates users
Visitor Location Register-Maintains temporary information onVisiting users.
Home Location Register –Maintains current customerLocation and service profile
GSM Registration
HLR/AC
VLR
Old VLR
Visited System
2) VLR queriesprevious VLR for user’s(actually the user’s smartcard) permanent ID.
Handset
1) Visited system detects handset,handset transmits temporary ID assignedby previous system.
3) The VLR sendsa registration messageto the HLR.
Mobile Networks: IP Approach• Mobile IP based on the notion that today’s Internet
protocols will evolve to provide most voice/data services: Connectionless protocols offer lower complexity implementation Distributed mobility management (no MSC!) Needs further enhancements for flow QoS support
IP ROUTER+ Mobility Ext
IP TERMINALIP ACCESS POINT
RadioAir Interface
IP/RSVP + “M”
IP HOST/SERVER
Standard IP
IP Pkts w/ DLC segmentsIP packets
Radio Microcell 1
Radio Microcell 2
Mobile Networks: ATM Approach• Mobile ATM a candidate architecture for telco scenarios
where an ATM access network is available: Support for service integration & flow QoS Connection-oriented framework suitable for dynamic handoff May be used for micro-level mobility, with mobile IP for macro-level
ATM SWITCH+ Mobility Ext
Mobile TERMINALATM ACCESS POINT
RadioAir Interface
Mobile ATM“M” UNI/NNI
HOST/SERVER
IPOA
ATM cells
Radio Microcell 1
Radio Microcell 2
MAC PDU’s
IP services+ voice
Application Data
Medium Access Control
Radio Transport Convergence Layer
Radio Physical Medium Dependent Layer
WirelessControl
RadioPHY
RadioAccess Layers
UserPlane
ControlPlane
Signaling, etc.+ mobility ext
..VC# 1 2 n
ATM Network Layer
SIG VC
Radiolink
control
Multiplexed user data
Radio Signal
Data Link Control (or “LLC”)
ATM Adaptation Layers
Mobile Networks : “+M” Protocol Stacks
Application Data
Medium Access Control
Radio Transport Convergence Layer
Radio Physical Medium Dependent Layer
WirelessControl
RadioPHY
RSVP +Mob Ext
..Flow # 1 n
IP Network Layer (incl.. Mob IP) Radiolink
control
Multiplexed user data
Radio Signal
Data Link Control (or “LLC”)
TCP/UDP/RTP
ControlFlow
Wireless ATM Protocol Stack Wireless IP Protocol Stack
Optional
Mobile IPRefer to:
http://computer.org/internet/v2n1/perkins.htM
http://www.ietf.org/html.charters/mobileip-charter.html
http://wwwtgs.ctit.utwente.nl/Docs/education/advanced/mobile/
Tutorials/MobileIPv6.pdf
Slides on Mobile IP at: http://ing.ctit.utwente.nl/WU4/Documents/47
Name, Address, Routing
• Name: is a location independent identifier of a host
• Address: indicates where a given host is located.
• Route: tells how to get to a destination
Mobility Problem: The Internet Viewpoint
• Internet addresses are assigned in a topologically significant manner.– A mobile host must be assigned a new
address when it moves.• Change host address connection
breaks.• Retain host address routing fails.• Host address must be preserved
regardless of its location.
Constraints
• Inter-operability with TCP/IP protocol suite.• Existing networking apps should run
unmodified on mobile hosts.• System should provide Internet-wide
mobility.• No modification on existing routing
infrastructure should be required.• Solution should be independent of wireless
hardware technology.• Solution should have good scaling properties.
IP’s subnet model vs. Mobility
• Terminals move from one IP subnet to another, but have the wrong “subnet prefix” for the destination subnet.
• Solution: two-tier IP addressing– The mobile keeps its static IP address,
but borrows the service of a “care-of-address” on whatever IP subnet it happens to be visiting.
– A “care-of-address”, offered by a mobility agent, can be shared by visiting mobiles.
Basic Mobile IP
• How does it work?– Agent discovery:
advertisement/solicitation– MH registration– Use of Care-of-Address (COA)– Proxy ARP (Address Resolution Protocol)– Packet tunneling– Triangle routing
Key components
HN
R1 R3
FN FNR2
HA
MH
MHCH
FAMobile Host:a host or router capableof changing its point ofattachment to the Internet
Foreign Network:a network, other than MA’s homenetwork, that MH is currently attachedto.
Corresponding Host:a host or router communicationgwith a mobile node.
Home Network:the network identifiedwith a mobile node
Home Address:MH’s permanent IP address,network ID of this address identifiesthe mobile’s home network. Home Agent:
a router attached to the MH’s home networkmaintains current location information for the MHis responsible for forwarding packets destined for theMH when MH is away from home.
Foreign Agent (FA)a router in the foreign network that the MH is visitingprovides routing services to the MH while registredde-tunnels datagram to MHmay serve as default router for outgoing packet from MH
Route Optimization
Route Optimization
• Provides a means for nodes to– cache the bindings of a mobile node– tunnel their own datagrams directly to the
care-of-address– bypass mobile node’s home agent during
datagram delivery
• Allow datagrams sent based on an out-of-data cached binding, to be forwarded directly to the mobile node’s new care-of-address.
Terminology• Binding cache
– a cache of mobility bindings of mobile nodes– maintained by CH for use in tunneling
datagrams to those mobile nodes.
• Binding update– a message indicating a mobile node’s
current mobility binding and its care-of-address.
• Registration lifetime– the time duration for which a binding is
valid.
Route Optimization
• Key features– Binding cache update– Smooth handoffs between foreign
agents– New messages
• binding update• binding request• binding warning• binding ack
Binding Cache Creation/Update
• At CH, if no binding cache exists– datagrams will be routed to MH via basic
mobile IP routing– home agent should then send a Binding
Update message to the original source node– CH will then create a binding cache for the MH
• At an FA, if MH has moved to a new FA and the old FA still receives tunneled datagrams– old FA send Binding Warning message to
HA to advise the change.
Foreign Agent Smooth Handoff
• As part of registration procedure, the mobile node may request its new FA to notify its previous FA on its behalf– a Previous Foreign Agent Notification extension is
included in the Registration Request message
• The new FA builds a Binding Update message and transmits it to the mobile node’s previous FA as part of registration, requesting an ACK from the previous FA
• Security association between old FA and MH are used for authentication of the binding update message.
Mobile ATM: System Model• “M” UNI/NNI protocol extensions provide integrated &
efficient support for mobility within ATM access network Functions include: location mgmt, handoff control, mobile
QoS/routing
ATM Network
Mobile ATMAccess Network
ReroutedConnectionAfter handoff
Crossoverswitch
TerminalMovement
ConnectionBefore Handoff
Connect (ATM Addr A)
Initial Location AL1
Next Location AL2
Location Mgmt providesmapping of A-> AL1, AL2
Handoff supportsDynamic reroutingOf active connections
User Addr A (permanent)
HO (BS1->BS2)
BS1
BS2
User Addr A
Mobile ATM: Location Mgmt• Location management can be integrated into existing ATM
connection procedures.... (external servers can also be used) simple extensions to current CONNECT, RELEASE IE’s, etc. no need for a-priori partitioning of mobile & static address space
ATMHost
move
setup (home_addr)
release (foreign_addr)
setup (foreign_addr,home_addr)
update
Homeswitch
Current Foreignswitch
(1)
(2)
(3)(4)
Mobile ATM: Handoff• Handoff can be implemented via modest extensions to existing
ATM UNI/NNI signaling... new signaling messages/IE’s for handoff initiation, COS select, etc. provides high-performance, scalable solution (compared with
external MSC, BSC, etc.)
move
handoffrequest
(1)
COSselect
ATMHost
CrossoverSwitch (COS)
addsubpath
tear downsubpath
handoffconfirm
GSMNetwork
Mobile ATMAccess Network
TerminalMovement
GSM
GSM/ATMgateway
GSM
Proxy M UNI
GSMradiolink
M NNI
M UNI
M NNI
GSM
Handoff & locmgmt within mobileATM cloud providedBy “M” UNI/NNI
GSM
GSMradiolink
HLR/VLR
GSM radioair interface
Proxymigration
M NNI
GSMradiolink
GSM
Proxy M UNI
GSMradiolink
Mobile ATM: Use with Cellular• For mobile ATM infrastructure, a “proxy M-UNI” can be used
at the AP for interworking with a non-WATM radio protocol... GSM (or other cellular access protocol) converted to M-UNI at
AP Mobile ATM provides handoff and location mgmt to GSM user
GSM
• Network part of broadband wireless system can be used as a generic infrastructure for various current & future radio access technologies --> platform for IMT2000/UMTS migration– Generic +M protocols supported by network routers/switches– Interworking function at AP converts to/from radio protocol
SWITCH/ROUTER+ Mobility Ext
IP/WLAN TERMINALAP
Wireless dataair interface
Generic “+M” Protocol
To Internetor Cellular/PCS
NetworkGateways
Wdata pkts
Cellular/PCSAir Interface
Mobile ATM: Use with 3G/WLAN