Exploiting Location and Context-Awareness to Support Proactive Handover in Heterogeneous Networks

EIS SEMINAR SERIES 2012

Glenford MappPrincipal Lecturer, Middlesex University


Motivation for the work Handover Classification Proactive-Handover Mathematical Framework Scenario Location information Wireless Footprinting Implications for future networking

infrastructure Future Plans


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


BACKBONE

ACCESS NETWORKS

WIRELESS NETWORKS


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


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



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


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


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


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


HANDOVER

IMPERATIVE ALTERNATIVE

REACTIVE PROACTIVE

KNOWLEDGE-BASED MODEL-BASED

NETPREF

USERPREF CONTEXT

SERVICES

UNANTICIPATED ANTICIPATED


HANDOVER EXECUTION LAYER

INPUT/OUTPUT LAYER

POLICY LAYER (PONDER)

WLAN GPRS LAN

L2 Triggers

HIGHER LAYERSInterface Information


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


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


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



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


Threshold Circle coverage

Real coverage

Exit coverage

Exit threshold circle

Handover threshold circle


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


TBVH simulation in OPNET Modeler:


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



NET A

NET B

NET A

NET B

NET A

NET B

Complete Coverage Two Networks Intersect Networks are Separate


Fatema Shaikh’s work



CF from upward handoverCE, EG, GH from downward handoverEF = CF – CE = Intersection Distance

Maximum CoveragePQ = AQ – APPQ = R1 – (AB – R2)PQ = R1 + R2 - AB


A

B

R1

R2

For Separate NetworksAB > R1 + R2

(Hard Handover)


A

B

C

S

T

NET A

NET B

NET C

Scenario

Three WLANs in a single UMTS cell


A

H1

C1

C2B

Y1Z1

E1

Y2

Z2

C

Y3

Z3

H3

E2

E3

S

TH2

Analysis





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


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


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



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


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





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


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


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


WIRELESSNETWORK

REQ (Time , TBVH, NDT)A

A

REQ (Time , TBVH, NDT)

B

B


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


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


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


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

Documents

Exploiting Location and Context-Awareness to Support Proactive Handover in Heterogeneous Networks