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VERTICAL HANDOVER/HANDOFF IN

HETEROGENEOUS WIRELESS NETWORKS

Saeeda Naz

Introduction Background and Concept of Handoff Management Vertical Handover/Handoff (VHO) VHO Algorithms Summary

Overview

Saeeda Naz Vertical Handover in Heterogeneous Wireless Networks

INTRODUCTION

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Universal Mobile Telecommunication System (UMTS)

Wireless Local Area Network (WLAN) Vehicular Ad Hoc Networks (VANETs) World Wide Interoperability for Microwave

Access (WiMAX) Wideband-CDMA (WCDMA) LEO Satellite Networks etc.

Integration of Various Heterogeneous Wireless Access Networks

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Ubiquitous Connectivity

Ability to exchange voice, video and data, anywhere and anytime, is the basis of a new mobile lifestyle

Customers increasingly desire to stay always connected and enjoy a wide variety of voice, data and multimedia services independent of their geographical locations

Continuous and ubiquitous connectivity is becoming interwoven with the lives of end-users, who increasingly rely on their mobile devices to provide them with best-in-class service

Motivation

Vertical Handover in Heterogeneous Wireless NetworksSaeeda Naz

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Multi-Homed Devices


7Mobility across Heterogeneous Wireless

Networks

Seamless Roaming

Towards 4G

Vertical Mobility


8A View of 4G Heterogeneous All-IP Wireless Networks

4G Heterogeneous All-IP Wireless Networks


BACKGROUND AND

CONCEPT OF HANDOFF

MANAGEMENT

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Different Wireless Networks are complementary to each other, their integration will allow mobile users to be connected using the best available access network that fits their needs

Handoff Management: It is the process by which a MT keeps its connection when it moves from one point of attachment (base station or access point) to another.

Handoff Management


Mobile Terminal(User)

Network(Operators)

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Types of Handoff

Horizontal (Homogeneous) Handoff (HHO)

Handoff or handover

Vertical (Heterogeneous) Handoff (VHO)


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Horizontal and Vertical Mobility


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Horizontal and Vertical Handoffs


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Need for Handoffs

Handoff may be required because

o A mobile device experiences a degradation in the radio signal

o An access point experiences a heavy traffic load, unable to maintain the negotiated QoS

o A mobile node has got a cost effective alternative

Forced Handoff

Willful Handoff


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Reduction of signaling and rocessing overhead.

Minimize packet loss, cost and delay (seamless HO).

QoS guarantees during the process and transfer of context.

High usability with anytime, anywhere connectivity.

Use of multimodal devices ( capable of supporting various type of network access technology).

Efficient use of network and MT resources.

Support for integrated service access from various providers, i.e., Allow inter-technology handoff (VHO).

Handoff Management Requirements


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Horizontal Handoff – mainly use received signal strength (RSS) to decide the handoff…

But Vertical Handoff ? RSS ?

Offered bandwidth ?

Price ? Handoff Metrics

Power consumption ?

Speed ?

Handoff Metrics


VERTICAL HANDOFF

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Vertical Handoffs

Vertical handoff refers to "when a nomadic user with a multi-interface terminal changes connection from one type of wireless access technology to another while maintaining an active session."


Vertical Handover in Heterogeneous Wireless Networks

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Wired NW

WLAN/WPAN

WiMAX GSM, CDMA,

UMTS

New Radio

CN

IP Backbone Network

Mobility Across Diverse Access Networks

Vertical Mobility

Vertical Mobility in Heterogeneous Networks

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Step 1: “System Discovery”

is the process of searching for available serving networks By MT.

Step 2: “Vertical Handoff Decision”

is the process of comparing serving networks and selecting the best one to be the target network through algorithms.

Step 3: “Handoff Execution”

is process of transfer data from the current network’s access point to the target network’s access point after making a decision.

Vertical Handoff (VHO) Process


ALGORITHMS

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The second step is of particular importance for the decision making than other two steps of vertical handoff and will directly affect the performance of vertical handoff.

So, efficient and reliable vertical handoff schemes and algorithms are required for seamless mobility between heterogeneous wireless access networks .

There are many schemes and decision algorithms of vertical handoff which base on different criteria metrics for decision. Some based on cost or bandwidth or RSS, or on combination of metrics.

Importance of Decision step


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VHD algorithms are classified into four groups based on the handover decision criteria1)RSS based algorithms 1.1) An adaptive lifetime based handover heuristic 1.2) An RSS threshold based dynamic heuristic 1.3) A traveling distance prediction based heuristic2) Bandwidth based algorithms 2.1) A QoS based heuristic 2.2) A signal to interference and noise ratio (SINR) based heuristic 2.3) A wrong decision probability (WDP) prediction based

heuristic

Classification of algorithm


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3) Cost function based algorithms 3.1) A multiservice based heuristic 3.2) A cost function based heuristic with normalization and 3.3)weights distribution 3.4) A weighted function based heuristic4) Combination algorithms 4.1) A multilayer feed forward artificial neural network 4.2) based heuristic 4.3) A method that uses two neural networks 4.4) A fuzzy logic based heuristic

Cont…


AN EXAMPLE OF INTEGRATION OF

WLAN AND CELLULAR

NETWORKS

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Vertical Handoff across different access networks

Cellular GSM/GPRS,

CDMA, UMTS

WLAN – Cellular Networks

Integration


WLAN – Cellular Networks Integration

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Important case of heterogeneous wireless networks integration is that of WLAN – Cellular Networks.


[Ref] M. Buddhikot, G. Chandranmenon, S. Han, Y. Lee, S. Miller and L. Salgarelli,“Integration of 802.11 and 3G Wireless Data Networks” in Proc. of IEEE

Infocom’03.


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Some interoperability open issues: When to switch?, VHO policies:

o WLAN to Cellular ~ Cellular to WLAN

Seamless handoff (level of integration).o Packet loss and VHO latency.

Load balancing between networks. QoS guarantees and transfer of context. Security and Authentication. Billing and revenue sharing. Implementation.



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Standardization efforts:

Both 3GPP and 3GPP2 are developing interworking solutions for WLANs as an extension of their radio access networks.

IEEE 802.21 Media Independent Handover (MIH) Group is working toward the seamless handoffs between:o IEEE 802.XX family.o IEEE 802.XX and 3G Cellularo Between 802.11 ESSs.

WLAN – Cellular Networks


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Although there have been various vertical handoff algorithms proposed in the literature but still it needs more and more research work in this domain to discover efficient and reliable handoff's scheme.

This should maintain the connectivity of the MT with maintaining quality of service and reducing costs and load balancing of target networks.

Vertical handover has added new dimensions to the handover process. The criteria metrics has become much more intricate.

Significant research efforts are being made to enable the handoff, but the task is extremely challenging. This is a very exciting phase in the domain of VHO for researcher and scholars, as the issues are still not solved.

Any solution that reduces the VHO delay and maintains the QoS can provide handsome increase in global link utilization and improved end user satisfaction.

Summary


SUMMARY

Saeeda Naz

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Although there have been various vertical handoff algorithms proposed in the literature but still it needs more and more research work in this domain to discover efficient and reliable handoff's scheme.

This should maintain the connectivity of the MT with maintaining quality of service and reducing costs and load balancing of target networks.

Vertical handover has added new dimensions to the handover process. The criteria metrics has become much more intricate.

Significant research efforts are being made to enable the handoff, but the task is extremely challenging. This is a very exciting phase in the domain of VHO for researcher and scholars, as the issues are still not solved.

Any solution that reduces the VHO delay and maintains the QoS can provide handsome increase in global link utilization and improved end user satisfaction.

Summary


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