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Exploiting Location and Context-Awareness for Proactive Handover in Heterogeneous Networks

This talk discusses the motivation, classification, and implications of proactive handover in heterogeneous networks, as well as a mathematical framework and future plans for network evolution.

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Exploiting Location and Context-Awareness for Proactive Handover in Heterogeneous Networks

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  1. Exploiting Location and Context-Awareness to Support Proactive Handover in Heterogeneous Networks Glenford Mapp Principal Lecturer, Middlesex University

  2. Outline of the Talk • Motivation for the work • Handover Classification • Proactive-Handover • Mathematical Framework • Scenario • Location information • Wireless Footprinting • Implications for future networking infrastructure • Future Plans

  3. Network Evolution • 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

  4. Internet Evolution BACKBONE ACCESS NETWORKS WIRELESS NETWORKS

  5. Heterogeneous Devices 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

  6. Vertical Handover (Side-effects) • 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

  7. Layer 5: Slow Adaptation of TCP After LAN->GPRS Handover

  8. The need for a New Framework • 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

  9. The Complete Y-Comm Framework PERIPHERAL NETWORK SECURITY LAYERS CORE NETWORK APPLICATION ENVIRONMENTS SAS SERVICE PLATFORM QBS QOS LAYER NETWORK QOS LAYER CORE TRANSPORT END SYSTEM TRANSPORT NTS NAS NETWORK MANAGEMENT POLICY MANAGEMENT CONFIGURATION LAYER VERTICAL HANDOVER NETWORK ABSTRACTION (MOBILE NODE) NETWORK ABSTRACTION (BASE STATION) HARDWARE PLATFORM (MOBILE NODE) HARDWARE PLATFORM (BASE STATION)

  10. This talk • 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/software/ycomm_research.aspx

  11. Handover Terms • 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

  12. Advanced Handover Classification HANDOVER ALTERNATIVE IMPERATIVE SERVICES NETPREF CONTEXT REACTIVE USERPREF PROACTIVE UNANTICIPATED ANTICIPATED MODEL-BASED KNOWLEDGE-BASED

  13. Reactive Policy: PROTON HIGHER LAYERS Interface Information L2 Triggers INPUT/OUTPUT LAYER POLICY LAYER (PONDER) HANDOVER EXECUTION LAYER LAN WLAN GPRS

  14. Proactive Policies • 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

  15. Proactive Policies • 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

  16. Proactive Policies 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

  17. Knowledge-Based Policy Management (Cambridge)

  18. Proactive Policies – Modelling Approach (Fatema Shaikh) • 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

  19. The Model-Based Handover

  20. Predictive Mathematical Model for TBVH(Simple Case) Movement of MS under BBS coverage (upward vertical handoff) • Introduction of additional functionality to Base Station at network boundary (BBS). • Distance between MS and BBS derived from location co-ordinates or • Estimated TBVH

  21. Simulation and Results TBVH simulation in OPNET Modeler:

  22. This work 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

  23. Law of Cosines

  24. Coverage Situations NET A NET A NET A NET B NET B NET B Two Networks Intersect Networks are Separate Complete Coverage

  25. Upward Handover Fatema Shaikh’s work

  26. Downward Handover

  27. Intersecting Networks Maximum Coverage PQ = AQ – AP PQ = R1 – (AB – R2) PQ = R1 + R2 - AB CF from upward handover CE, EG, GH from downward handover EF = CF – CE = Intersection Distance

  28. Separate Networks A R1 R2 B For Separate Networks AB > R1 + R2 (Hard Handover)

  29. Scenario Three WLANs in a single UMTS cell NET A A NET B S NET C B C T

  30. Analysis C1 E1 Y2 Z1 A Y1 Y3 H1 C2 S B E2 C H3 E3 H2 T Z2 Z3

  31. Results

  32. Checking Results

  33. Checking Results

  34. Summary • 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

  35. Location of Network Infrastructure • 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

  36. Estimating Handover Radius • 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

  37. Comparison with HR=104m

  38. Implications • 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

  39. Concept of Wireless Footprinting • 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

  40. Wireless Footprinting

  41. Using the WF System

  42. Ontology Used to Build the System

  43. WS-continued 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

  44. Next Step • 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

  45. Brave New World GPS Location, Speed, direction NDT TBVH New QoS New IP Connections (QoS) Polling CORE NETWORK Done NETWORK MANAGEMENT LAYER Send to Mobile TOPOLOGY, RESOURCES, QoS POLICY MANAGEMENT LAYER DECISION HANDOVER (BASE-STATION, 3G, QOS, TBVH, NDT) DO IT CONFIGURABLE LAYER ACQUIRE CHANNEL (3G Base-station , QOS, TBVH, NDT) VERTICAL HANDOVER LAYER ACQUIRE RESOURCES ( 3G Base-station, QOS, TBVH, NDT) DO IT NETWORK ABSTRACTION LAYER BASE-STATION NETWORK ABSTRACTION LAYER DATA CHANNNEL = 3G 3G=ACTIVE WLAN=PASSIVE WiMAX= PASSIVE CHANNEL ACQUIRED L2 events Media Info 3G WLAN WiMax 3G WLAN WiMax

  46. Scenario WIRELESS NETWORK REQ (Time , TBVH, NDT) A A B REQ (Time , TBVH, NDT) B

  47. Single Channel Analysis 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

  48. Single Channel Analysis • 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

  49. Results of Request • 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

  50. Future Plans • 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

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