A QOS oriented VHO scheme for WLAN and WIMAX overlay networks

1. Under the Esteemed Guidance of
Mrs. S.J.Saritha
Assistant Professor & HOD
By
CH.Srilakshmi Prasanna
(11191D5801)

2. 





Introduction
Handoff Process
Horizontal Handoff Process
Vertical Handoff Process
Conclusion
References

3. 




Wireless communication system
Cellular Networks
Handoff
Horizontal Handoff
Vertical Handoff

4. 



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.

5. 
Goals
◦ provide coverage over a large area
◦ provide coverage to a large number of users
◦ maintain an acceptable level of quality

6. 

Limit on number of users due to frequency
limitations (only so much spectrum)
Some way to reuse frequencies?

7. 
Cellular Systems to the rescue!

8. 
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

9. 
Frequency reuse
◦ The same frequencies are reused in multiple cells.

10. 

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.

11. 
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.

12. 
Handoffs must be:
◦ performed quickly
◦ performed infrequently
◦ imperceptible to users
◦ performed successfully

13. 
Types of Handoff

15. 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

16. 



Upward and Downward Handoffs.
Hard and soft Handoffs.
Imperative and Alternative Handoffs.
Mobile Controlled and Network Controlled Handoffs.
MCNA,NCMA

17. 
Hard and soft Handoffs

18. 
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.

19. 


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.

20. 
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.

22. • High Delay
• Signal breakage
• Less packet delivery

23. 
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.

24. WiMax Unit
WLAN Unit
Delay Analyzer
Handoff controller
Wimax<--->WLAN
Bandwidth
estimation

25. 
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.

26. 
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

27. =(1−
)
=(1−
)
Delay calculation for WIMAX
= + + +
Bandwidth for WLAN
= −
/ +12 , ( −1)
Delay for WLAN = + = 21− +
}
 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.

28. Parameters
Values
Wi-MAX nodes
1
WI-FI nodes
3
Mobile nodes
11
Routing protocol
AODV
WI-FI coverage
100m
Wi-MAX coverage
Simulation time
400m (for testing only)
10s

29. Table: Different Simulation times for X-graph
Simulation time
Previous
Send pkts
Received
pkts
Enhanced
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

30. RESULT
•Throughput performance
25000
throughput kb/s
20000
15000
pre
10000
enhanced
5000
0
10
20
30
40
50
60
70
80
90
100
simulation time (sec)
•Packet Delivery Ratio
Packet delivery ratio
1
0.9995
0.999
0.9985
pre
0.998
enhanced
0.9975
0.997
10
20
30
40
50
60
70
simulation time
80
90 100

31. 0.005
0.004
delay Sec
Average End -to-End
• Average End-to-End Delay
0.003
0.002
pre
0.001
enhanced
0
10
20
30
40
50
60
70
80
90
100
Simulation time
packet loss ratio %
• Packet Loss Ratio
0.0025
0.002
0.0015
0.001
pre
0.0005
enhanced
0
10
20
30
40
50
60
70
simulation time
80
90
100

32. 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.