exploiting location and context-awareness to support proactive handover in heterogeneous networks
DESCRIPTION
Exploiting Location and Context-Awareness to Support Proactive Handover in Heterogeneous Networks. Glenford Mapp Principal Lecturer, Middlesex University. Outline of the Talk. Motivation for the work Handover Classification Proactive-Handover Mathematical Framework Scenario - PowerPoint PPT PresentationTRANSCRIPT
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Motivation for the work Handover Classification Proactive-Handover Mathematical Framework Scenario Location information Wireless Footprinting Implications for future networking
infrastructure Future Plans
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The Internet will evolve in a physical sense Core of the network
◦ Super-fast backbone (optical switching, etc)◦ Fast access networks (MPLS, ATM)
Peripheral Wireless Networks◦ Errors due to fading, etc; not just congestion◦ Handover
Consequences Degradation of end-to-end arguments
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Devices will have more than one wireless interface.
Vertical handover – switching between different network interfaces to provide seamless connectivity
Vertical handover is good but it introduces a lot of QoS issues because the different wireless networks have different qualities of service
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Affects your connections ◦ Some protocols react badly with respect to
handover. Affects your applications
◦ Need to think through how Quality-of-Service affects applications
Encapsulate these ideas in a Framework
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New framework◦ We need to control network interfaces generically◦ Make mobility support explicit
Vertical handover can have tsunami effects◦ Merge network and transport services ◦ Make QoS support explicit
Provide a way for applications to negotiate with the network
◦ Security Goal: Integration of Communication,
Mobility, Quality-of-Service and Security
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HARDWARE PLATFORM (MOBILE NODE)
HARDWARE PLATFORM (BASE STATION)
NETWORK ABSTRACTION (MOBILE NODE)
NETWORK ABSTRACTION (BASE STATION)
VERTICAL HANDOVER
POLICY MANAGEMENT
END SYSTEM TRANSPORT
QOS LAYER
APPLICATION ENVIRONMENTS
CONFIGURATION LAYER
NETWORK MANAGEMENT
CORE TRANSPORT
NETWORK QOS LAYER
SERVICE PLATFORM
CORE NETWORKPERIPHERAL NETWORK
SAS
NTS
NAS
QBS
SECURITY LAYERS
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Can’t explain everything about Y-Comm It’s too big
Several people at Middlesex work on it:◦ Mahdi Aiash : Security◦ Fragkiskos Sardis: Mobile environments
Also Cambridge, Loughborough and USP Concentrate on the Handover
◦ Ferdinand Katsriku & MSc students See Y-Comm Research Webpage: http://www.mdx.ac.uk/research/areas/softwa
re/ycomm_research.aspx
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Hard vs Soft Handovers◦ Hard: - break before make◦ Soft – make before break
Network vs Client Handovers◦ Network – network in control (current)◦ Client – future (Apple’s patent)
Upward vs Downward◦ Upward – smaller to bigger coverage◦ Downward – bigger to smaller
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HANDOVER
IMPERATIVE ALTERNATIVE
REACTIVE PROACTIVE
KNOWLEDGE-BASED MODEL-BASED
NETPREF
USERPREF CONTEXT
SERVICES
UNANTICIPATED ANTICIPATED
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HANDOVER EXECUTION LAYER
INPUT/OUTPUT LAYER
POLICY LAYER (PONDER)
WLAN GPRS LAN
L2 Triggers
HIGHER LAYERSInterface Information
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Proactive Policy Management◦ The mobile node can know or estimate the
network state at a given point before it arrives at that point
◦ Proactive Policies allow us to maximize the use of available channels provided you know the amount of time a channel will be available.
◦ That time is known as: Time before vertical handover (TBVH) Can significantly reduce packet loss during all vertical
handovers
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Proactive policies can themselves be divided into 2 types
Proactive knowledge-based systems◦ Knowledge of which local wireless networks are
operating at a given location and their strengths at that point
◦ We also need a system to maintain the integrity, accessibility and security of that data
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Knowledge-based approach Gather a database of the field strengths for
each network around Cambridge Need to maintain the database and also
know how the results might be affected by seasonal effects
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Using a simple mathematical model Define a radius at which handover should
occur Find out how much time I have before I hit
that circle, given my velocity and direction Calculate TBVH
Used simulation (OPNET) Can be used in the real world as well as in
simulation
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Threshold Circle coverage
Real coverage
Exit coverage
Exit threshold circle
Handover threshold circle
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Introduction of additional functionality to Base Station at network boundary (BBS).
Distance between MS and BBS derived from location
co-ordinates or
Estimated TBVH
)log(10 lRSSdB
v
xdxdrTBVH
cossin 222
Movement of MS under BBS coverage (upward vertical handoff)
BBS
MS
r
dz
x
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Extends Fatema’s work which only looked at upward handover
Looks at providing a complete mathematical framework
Uses the Law of Cosines Needs accurate location information plus
handover radius
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NET A
NET B
NET A
NET B
NET A
NET B
Complete Coverage Two Networks Intersect Networks are Separate
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CF from upward handoverCE, EG, GH from downward handoverEF = CF – CE = Intersection Distance
Maximum CoveragePQ = AQ – APPQ = R1 – (AB – R2)PQ = R1 + R2 - AB
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If the mobile node knows:◦ Its location, direction and velocity
Via GPS, accelerometers◦ The location of networking infrastructure
Type of radio network, position of the Access Points◦ A good estimation of the Handover Radius
Hard to do Then we can calculate the optimal time to
handover over a large area using this mathematical framework
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Mobile Operators◦ Location of Base-Stations tends to be difficult to
obtain. Commercially sensitive
Location of WLANs ◦ Ad-hoc arrangements◦ Almost impossible; need to do wardriving
Growing need to address this issue IEEE 802.21:Media Independent Information Service
(MIIS) Cognitive Radio is also going to change this
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Need 4 things◦ Location of the Transmitter◦ The power at the transmitter◦ Propagation model◦ The signal threshold at which handover should
occur Depends on the wireless receiver in the Mobile Node
More expensive the better Most WLAN receivers can do -70-85dB Mobile phones: around -120 dB
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Need better propagation models Propagation Models
◦ Semi-static Models: Free Space, Okumura and Hata Models Less dependent on specific conditions
◦ Finite-element propagation models Arshad and Katsriku
They take into account surroundings and specific conditions
Need for a more dynamic approach◦ More context and location awareness
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Let mobile nodes store information about their location, the signal strengths and other measurements in the core network
Make information on previous journeys available
Also this information to be shared with other mobile uses◦ Need to make sure that we don’t forget privacy
Developed at USP
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System has been built and can be used. So we put the software on mobile phones and it uses the WF Server
This will allow us to look at building a better propagation model that is more tuned to location and context of mobile nodes
More dynamic; based on continuous measurements
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Explore the effect of TBVH and NDT on channel allocation strategies
Could be the real game-changer for mobile operators
A mobile node is able to say much more when requesting a channel◦ Will also know TBVH and NDT◦ Allow better channel allocation
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POLICY MANAGEMENT LAYERDECISION HANDOVER
(BASE-STATION, 3G, QOS, TBVH, NDT)
GPSLocation,
Speed, direction
Connections (QoS)
VERTICAL HANDOVER LAYERACQUIRE RESOURCES
( 3G Base-station, QOS, TBVH, NDT)
NETWORK MANAGEMENT LAYERSend to Mobile
TOPOLOGY, RESOURCES, QoS
NDTTBVH New QoSNew IP
CONFIGURABLE LAYERACQUIRE CHANNEL
(3G Base-station , QOS, TBVH, NDT)
NETWORK ABSTRACTION LAYERBASE-STATION
CHANNEL ACQUIRED
DO IT
NETWORK ABSTRACTION LAYERDATA CHANNNEL = 3G
3G=ACTIVE WLAN=PASSIVE WiMAX= PASSIVE
3G WLAN WiMax 3G WLAN WiMax
Done
DO IT
L2 eventsMedia Info
CORE NETWORKPolling
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MNA needs channel at (Time + TBVH) A
MNA releases channel at (Time + TBVH + NDT)A
MNB needs channel at (Time + TBVH)B
MNB releases channel at (Time + TBVH + NDT)B
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No Contention◦ (Time + TBVH)A < (Time + TBVH)B
◦ (Time + TBVH + NDT)A < (Time + TBVH)B
Contention: Two Types: Partial and Total◦ (Time + TBVH)A < (Time + TBVH)B
◦ (Time + TBVH + NDT)A > (Time + TBVH)B
◦ Partial Contention (Time + TBVH + NDT)A < (Time + TBVH + NDT)B
◦ Total Contention (Time + TBVH + NDT)A >= (Time + TBVH + NDT)B
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Request Granted as requested◦ Channel granted at (Time + TVBH)A
◦ Channel released at (Time + TBVH + NDT)A
Request Granted but modified (for B)◦ Channel granted at (Time + TBVH + NDT)A
◦ Channel released at (Time + TBVH + NDT)B
Request not granted◦ Force handover to other network(s)◦ MN node no longer stuck in queue
Much better use of core resources
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Basic mathematical framework◦ Develop a program for mobile phones
Better propagation models◦ Use Wireless Footprinting
Investigate the implications for the core infrastructure◦ New multi-channel allocation scheme based on
TBVH and NDT◦ Quantify improvement
Show mobile operators how they can provide much better services in this new context