1. Mobile IPv6-based Efficient Vertical Handoff Approach for Heterogeneous Wireless Networks
Ben-Jye Chang Ph.D. (張本杰 博士)
Department of Computer Science & Information Engineering
Chaoyang University of Technology
Taichung, Taiwan
NSC E

2. Outline Introduction Related Works Motivations
Adaptive cost-based vertical handoff with predictive RSS
Numerical results
Conclusions

3. What is handoff? (Introduction)
Maintaining connections or communications when mobile node moves to other cell.
Advantages
Do not disconnect the original connections
Support Quality of Service (QoS)
Reduce cost
Disadvantages
(PS, CS) Extra handoff signaling and handshaking with new cell
(PS) Need Mobile IP for solving addressing issue

4. Heterogeneous Wireless Networks

5. Types of Handoff Horizontal handoff Vertical handoff
Moving to the network that with the same access network protocol
Vertical handoff
Moving to the network that with different access network protocols

6. Why needs Vertical Handoff ?
Two most popular networks
Cellular networks
Wireless LANs (i.e., WLANs)
Comparison between Cellular Networks and WLANs
Network Characteristics
Cellular networks (GPRS/3G/B3G/4G)
WLANs
( a/b/g/e)
Coverage
Ubiquitous (N×101 Km, BS radius)
Local (N×1001 m, AP radius)
Bandwidth
Low (30K-2Mbps)
High (2~54MMbps)
Access cost
High
Low
Deployment Cost
Very High
Security
More Secure
Weak (WEP-based)
Application
CS, PS (VoIP)
PS (VoIP)

7. What are the challenges to vertical handoff ?
Horizontal handoff algorithms are not suitable for vertical handoff
In VH, no comparable signal strengths associated with them
The roaming networks are hybrid networks
Ping-pong effect
High data rate
Mobile IP Issue
QoS mapping between two different protocols

8. Related Works RSS-based handoff algorithm RSS-Threshold (RSS-T)
1. G.P. Pollini, “Trends in handover design,” IEEE Communications Magazine, Vol. 34, Issue 3, pp.82-90, March 1996.

9. Related Works (cont.) RSS-based handoff algorithm
RSS-Hysteresis (RSS-H)
2. N. Zhang, and J.M. Holtzman, “Analysis of handoff algorithms using both absolute and relative measurements,” IEEE Transactions on Vehicular Technology, Vol. 45, Issue 1, pp , Feb

10. Related Works (cont.) RSS-based handoff algorithm
RSS-Hysteresis with Threshold (RSS-HT)
3. P. Marichamy, S. Chakrabarti, and S.L. Maskara, “Performance evaluation of handoff detection schemes,” TENCON 2003, Vol. 2, pp , Oct

11. Related Works (cont.)
4. K. Pahlavan, P. Krishnamurthy, A. Hatami, M. Ylianttila, J.P. Makela, R. Pichna, and J. Vallstron, “Handoff in hybrid mobile data networksfs,” IEEE Personal Communications, Vol. 7, Issue 2, pp , April 2000.
RSS-T + Neural network-Based Algorithm
5. Hongyang Bing, Chen He, and Lingge Jiang, “Performance analysis of vertical handover in a UMTS-WLAN integrated network,” IEEE PIMRC 2003, Vol. 1, pp , Sept
RSS + Distance (mobile – AP)
6. H.J. Wang, R.H. Katz, and J. Giese, “Policy-enabled handoffs across heterogeneous wireless networks,” IEEE Mobile Computing Systems and Applications Conference, pp , Feb
7. J. McNair and Zhu Fang, “Vertical handoffs in fourth-generation multinetwork environments,” IEEE Wireless Communications, Vol. 11, Issue 3, pp. 8-15, June 2004.
Cost function ( cost = ln (1/ bandwidth) )

12. Motivations
Propose an efficient VH algorithm for heterogeneous wireless networks
Minimize the number of vertical handoffs
Support QoS
Maximize network utilization
Minimize access cost

13. Adaptive Cost-based Vertical Handoff with Predictive RSS
Two-step approach
Predict RSS with hysteresis
Determine the optimal wireless network for handoffing

14. Hysteresis with two-threshold
Determine
Optimal WLAN
Determine
Optimal WLAN
+ :Reducing the Ping-pong effect

15. 1. Predict RSS with hysteresis
Predictive algorithm
Advantages
Accurately catch the trend of RSS
Accurately predict RSS for making decision of VH

16. 2. Determine the optimal wireless network
General function:

17. COL WLAN Cost Function
we adopt the COL (Competitive On-Line ) approach for defining WLAN cost
sets the WLAN cost as an exponential function of current residual bandwidth of the link
state-dependent cost function
In most of the past research on hierarchical routing problem, the link costs were not well-defined.
However, the definition of link cost affects the performance of a hierarchical routing algorithm.
In this paper, we adopt the Competitive On-Line approach for defining link cost.
[slide]

18. WLAN Cost Function (cont.)
COL WLAN cost function,
 : a chosen constant parameter
Cap( ) : the capacity of WLAN n
COL WLAN cost for class k call,
The least cost WLAN will be selected as the optimal WLAN for vertical handoff
W of I is equal to u to the power of I over cap of I minus one, where u is a chosen constant.
Class k COL link cost is defined as p of I.
The path cost is sum of the costs of all links along the path

21. Mobile IPv6 Fast Vertical Handoff from 3G to WLAN

22. Mobile IPv6 Fast Vertical Handoff from WLAN to 3G

23. Numerical results Simulation Parameters Performance Metrics

24. Simulation Parameters
Topology
1000*1000 (m2)
# of Access Points
1, 5, 10, 15, 20, RAND[1~NDS] (APS)
# of Mobile Nodes
10, 20, 30, 40, 50 (NDS)
Velocity
random [0-5] (m/s)
Bandwidth
CAP_3G : 384Kbps
CAP_WLAN : 2000K bps
Traffic classes (3G/WLAN)
VBR : 10~384/10~1600Kbps (Pareto dist.)
CBR : 50/100Kbps (Poisson process)
WLAN Radius
100m
3G Radius
Always covers

25. Performance Metrics The number of vertical handoffs
Dropping probability
Network throughput

26. The number of vertical handoffs under different arrival rate (NDS=50, APS=10)
smooth
congestion

27. Dropping probability under diff. arrv. (NDS=50, APS=10)
No dropping
smooth
congestion

28. Network throughput under diffent arrv. (NDS=50, APS=10)
Closely
smooth
congestion

29. The number of vertical handoffs under various mobilities (NDS=50, APS=10)
slow
fast

30. Dropping probability under various mobilities (NDS=50, APS=10)
No dropping
slow
fast

31. Network throughput under various mobilities (NDS=50, APS=10)
Closely
fast
slow

32. The number of vertical handoffs under different NDS (APS=10, λ=10)

33. Dropping probability under different NDS (APS=10, λ=10)
No dropping

34. Network throughput under different NDS (APS=10, λ=10)
Closely

35. Conclusions
we proposed an adaptive cost-based with predictive RSS vertical handoff approach to determine the optimal wireless network for handoff in heterogeneous wireless networks.
A two-phase procedure
The predictive RSS with hysteresis phase
The determination of optimal wireless network phase
The proposed approach outperforms other approaches in
The least number of vertical handoffs while yielding competitive throughput
Yielding none dropping probability, which meets the characteristic of an optimal vertical handoff in heterogeneous wireless networks.

36. Q & A Thanks changb@mail.cyut.edu.tw
Above is my presentation of this paper, any question?

37. RSS_B2>RSS_B1, Switches to cell B2
Horizontal handoff
Receives B1 & B2 signal
In cell B1
RSS_B2>RSS_B1, Switches to cell B2

38. VHO Determine Algorithm. Switches to WLAN
Vertical handoff
In 3G, receives AP signal
In 3G
VHO Determine Algorithm. Switches to WLAN
In WLAN