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 changb@mail.cyut.edu.tw NSC-93-2213-E-324-018

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

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

Heterogeneous Wireless Networks

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

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 (802.11 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)

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

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.

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.174-179, Feb. 1996.

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. 643 - 646, Oct. 2003.

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. 34-47, 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.187-191, Sept. 2003. 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. 51 - 60, Feb. 1999. 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) )

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

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

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

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

2. Determine the optimal wireless network General function:

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]

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

Mobile IPv6 Fast Vertical Handoff from 3G to WLAN

Mobile IPv6 Fast Vertical Handoff from WLAN to 3G

Numerical results Simulation Parameters Performance Metrics

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

Performance Metrics The number of vertical handoffs Dropping probability Network throughput

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

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

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

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

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

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

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

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

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

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.

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

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

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