A QoS Oriented Vertical Handoff Scheme for WiMax/WLAN Overlay Networks

Under the Esteemed Guidance of

Mrs. S.J.Saritha

Assistant Professor & HOD

By

CH.Srilakshmi Prasanna

(11191D5801)

Outline

Introduction Handoff Process Horizontal Handoff Process Vertical Handoff Process Conclusion References

Introduction

Wireless communication system Cellular Networks Handoff Horizontal Handoff Vertical Handoff

Wireless Comm. Systems Mobility is the most important feature of a

wireless cellular communication system. A single tower at the center called a base

station (BS). Powerful transmitter attached to top of BS. Coverage area increased by making tower

taller and/or increasing transmission power.

Wireless Comm. Systems (contd.)

Goals◦ provide coverage over a large area◦ provide coverage to a large number of users◦ maintain an acceptable level of quality

Problem!

Limit on number of users due to frequency limitations (only so much spectrum)

Some way to reuse frequencies?

Solution! Cellular Systems to the rescue!

Cellular System Cellular concept:

◦ Many small base stations◦ Each BS communicates with mobiles in its

respective cell.◦ MSC (Mobile Switching Center) is responsible for

coordinating communications within the system Goals:

Large coverage area High call quality High capacity

Cellular System (cont’d)

Frequency reuse ◦ The same frequencies are reused in multiple cells.

Question

What happens when mobile moves from one cell to another? Handoff!!

◦ The process of transferring a mobile user from one channel or base station to another.

Heterogeneous wireless communication system is used to access the communication services anytime, anywhere with best QOS at minimum cost.

Heterogeneous wireless networks has different access technologies, overlapping and coverage, and network architecture, protocols for transport, routing and mobility management.

Different operators offers different services like voice,video,multimedia,text to mobile users.

Because of these variations, when the mobile users moves there is a need to handover the communication channel from network to another by considering its features and also the user requirements.

Heterogeneous wireless communication system

Handoff (Handover) Characteristics

Handoffs must be:◦ performed quickly

◦ performed infrequently◦ imperceptible to users◦ performed successfully

Types of Handoff

Types of Handoff

Vertical And Horizontal Handoff scheme

1. Handoff Initiation:- In this phase ,information is collected about the network from different layers like Link layer, Transport layer, Application layer which gives information such as RSS, Bandwidth, link speed, throughput, cost, power, user preferences and network subscription.

2. Handoff Decision:- In this phase decision is depend on the information collected during initiation phase.

3. Handoff Execution:-Authentication and authorization

Vertical Handoff Process(VHO)

Upward and Downward Handoffs.

Hard and soft Handoffs. Imperative and Alternative Handoffs. Mobile Controlled and Network Controlled Handoffs.

MCNA,NCMA

Classification of VHO

Classification of VHO

Hard and soft Handoffs

VHO Decision Making Parameters

VHO can be initiated for convenience rather than connectivity reasons.

1) Network -Related Parameters:- Bandwidth,RSS,Cost,Security.

2) Terminal-Related Parameters:-Velocity, Battery power, Location information.

3) User -Related Parameters:- user profile and preferences.

4) Services-Related Parameters:-Services capacities,QOS etc.

A technology should satisfy the following requirements. Bandwidth and delay and also user preferences such as 1. Price 2. power consumption or speed.

If the service provided by the connected network cannot satisfy the requirements, the station should switch to another network for better performance.

Proposed VHO scheme will facilitate the above mentioned

requirements.

Problem Statement

Existing System

In the existing cellular/WLAN overlay systems, there are two types of interworking architectures: tightly coupled where WLAN works as a radio access network of cellular system, and loosely coupled where different networks are independently deployed but integrated at network layer.

In previous QoS based VHO methods for overlay networks, QoS parameters are considered in handoff decisions.

The handoff procedures are normally started when the stations move across the border of WLANs.

As a result, both the fixed stations and the mobile stations within overlapped areas cannot benefit from VHOs.

Existing system

DISADVANTAGES

• High Delay

• Signal breakage

• Less packet delivery

Proposed System

In this project, we investigate the integration and VHO issues in WiMAX/WLAN overlay networks.

We address architecture to support our VHO scheme. We propose a tightly coupled interworking structure. And proactive handoff method

To achieve a proactive handoff, we design a VHO manager (VHOM) to control the whole handoff process, which works on the medium access control (MAC) layers of WiMAX and WLAN interfaces at the station.

Block Diagram of VHOM

WiMax Unit

Handoff controller

Wimax<--->WLAN

WLAN Unit

Delay Analyzer Bandwidth estimation

Primary network◦ Primary users:

Primary users have the license to operate in certain spectrum bands

◦ Primary base station: Controls the access of primary users to spectrum

Secondary network◦ Secondary users:

Secondary users have no licensed bands assigned to them.

◦ Secondary base-station: A fixed infrastructure component with cognitive radio capabilities and

provides single hop connection to secondary users.

Proposed System

Movement-AwareV ertical Handoff Algorithm

Step1:

Initializing a mobile node it can access both WiMAX/WLAN.

Initialize WiMAX/ WLAN networks. Step2:

Node will check the available networks. Step3:

If {network available} {

If {only one network} {

Get communication from that.

}

else

{

For {each network}

{

Checks which are the best networks in terms of Bandwidth and packet delay

Theory of Bandwidth calculation for Wi-MAX is given as follows.

Bandwidth calculation for Wi-MAX

𝐵𝑑=(1− ) =(1− )𝐴𝐴𝑠𝑑𝑠𝑑 𝛿𝑑𝑠𝑑𝑇𝑓 𝐵𝑢 𝐴𝐴𝑠𝑢𝑠𝑢 𝛿𝑢𝑠𝑢𝑇𝑓 Delay calculation for WIMAX 𝑡= + + +𝑡𝑠 𝑡𝑞 𝑡𝑚 𝑡𝑡 Bandwidth for WLAN = − / +12 , ( −1)𝐵𝑊 𝐵𝑜 𝐿𝑁𝐴𝑉 𝑇𝑛 𝑇𝑛 𝑐 𝑁 Delay for WLAN = + = 21− + 𝑡 𝑡𝑞 𝑡𝑎 𝑡𝑎 𝑡𝑎 𝑡𝑎} Step 4: Mobile node compares both networks VHOM selects best

Step 5: If no AP or BS detected Checks whether any other mobile station available AP or BS connection and have enough bandwidth limit. If mobile station detected with enough quality and then switch to mobile station communication.

Step 6: Else No communication.

MAV Algorithm

Parameters Values

Wi-MAX nodes 1

WI-FI nodes

3

Mobile nodes 11

Routing protocol AODV

WI-FI coverage 100m

Wi-MAX coverage 400m (for testing only)

Simulation time 10s

Network Model Values

Simulation time Previous EnhancedSend pkts Received

pkts Send pkts Received pkts

10s 20052 20013 27540 27502

20s 57130 57050 80107 80028

30s 109046 108924 155523 155402

40s 174950 174786 252908 252745

50s 254848 254642 372309 372103

60s 348759 348510 513708 513459

70s 456661 456370 677104 676813

80s 578576 578242 862521 862187

90s 714482 714105 1069935 1069559

100s 864400 863980 1528759 1528299

Table: Different Simulation times for X-graph

RESULT•Throughput performance

10 20 30 40 50 60 70 80 90 1000

5000

10000

15000

20000

25000

preenhanced

simulation time (sec)

thro

ughp

ut k

b/s

•Packet Delivery Ratio

10 20 30 40 50 60 70 80 90 1000.997

0.9975

0.998

0.9985

0.999

0.9995

1

preenhanced

simulation time

Packet

delivery

rati

o

• Average End-to-End Delay

10 20 30 40 50 60 70 80 90 1000

0.00050.001

0.00150.002

0.00250.003

0.00350.004

0.0045

preenhanced

Simulation time

Avera

ge E

nd -

to-E

nd

dela

y S

ec

• Packet Loss Ratio

10 20 30 40 50 60 70 80 90 1000

0.0005

0.001

0.0015

0.002

0.0025

preenhanced

simulation time

packet

loss r

ati

o %

Conclusion

MAV decision Algorithm provide the mobile nodes with best QOS at minimum cost according to the user preferences.

FUTURE WORK

To provide best network services several parameters to be considered such as TCP performance issues, security issues.

THANK YOU