Modularized Two-Stages Vertical Handoff Scheme

in Integration of WWAN and WLAN Shimin Li Ying Wang

Presented byShimin Li E&CE750

Second part of presentation of our report

Recall the first part of presentation

Motivation and Objective Overview of WWAN and WLAN Integration of WWAN and WLAN Modularized Vertical Handoff Scheme

Decision module

Presentation Overview

Mobile IP Vertical Handoff Delay Related works Solutions Modularized Vertical Handoff Scheme

Action Module Performance Analysis Discuss Conclusion

Mobile IP

This diagram comes from ECE750 lecture slides

Mobile IP cont’d

Basic Mobile IP MN has a permanent IP address When moving to foreign network, MN detects a FA

and obtains a CoA, and registers the CoA with HA HA tunnels all packets of MN to FA or MN itself

using the CoA CoA can be Foreign Agent CoA or Co-located CoA

Mobile IP cont’d

This diagram comes from ECE750 lecture slides

Mobile IP cont’d

Optimized Mobile IP CN requests the current location of MN from HA. HA

returns the CoA of MN via an update message. Then CN caches the CoA and send packets directly to the current foreign agent FA or MN itself. Encapsulation of data for tunneling to the CoA is now done by CN, not HA

Solve triangular routing problem

Mobile IP cont’d

Assumption about MIP Vertical handoff scheme is based on MIPv4 CoA is a Foreign Agent CoA, not Co-located CoA

Vertical Handoff Delay

Vertical Handoff Delay cont’d

Definition Vertical handoff delay = D1 + D2 + D3

Analysis D1 depends on movement and is out of control, we assume

that D1 is relatively small D2 and D3 can be minimized using intelligent handoff scheme

Related work

Proposed mechanisms addressing reducing delay H. Park et al. reduced delay by adding two structures to the

integration: Mobile Agent and Subnet Agent S. Sharma et al. introduced OmniCon: a MIP-based vertical

handoff system for integration of WLAN and GPRS[2] Ye Min-hua et al. used RSS triggering and multi-tunneling to

address WLAN/GPRS integration based on Basic MIPv4[3] Q. Zhang et al. proposed a subscription/notification service in

vertical handoff system based on MIPv4 to handle simultaneous movements and provide transparency to NAT[4]

Solutions For minimizing D2

Sense physical and MAC layer For minimizing D3

Divide handoff procedure into two steps Perform advance registration Allow MN to communicate with FAnew while still connected to FAold

For reducing packet loss Copy and tunnel packets for MN to FAnew even before handoff has

been finished For easy implementation and application transparency

Vertical handoff is based on MIP Only modify the entities of MIP such as MN, HA, and FA Modularize the handoff system

Modularized Vertical Handoff Scheme

ModularizationDecision ModuleAction Module

Recall the Decision Module

Trigger handoff actions How?

By sending messages to Action Module: Per-handoff message Handoff message

Action Module

Perform vertical handoff actions Per-handoff actions Handoff actions Undo actions

Triggered by messages from Decision Module

Action Module cont’d

Per-handoff actions Triggered by Per-handoff messages Four scenarios:

From WWAN to WLAN based on Basic Mobile IP From WWAN to WLAN based on Optimized Mobile IP From WLAN to WWAN based on Basic Mobile IP From WLAN to WWAN based on Optimized Mobile IP

Action Module cont’d

Action Module cont’d

Action Module cont’d

Action Module cont’d

Action Module cont’d

Handoff actions Triggered by Handoff messages Four scenarios:

From WWAN to WLAN based on Basic Mobile IP From WWAN to WLAN based on Optimized Mobile IP From WLAN to WWAN based on Basic Mobile IP From WLAN to WWAN based on Optimized Mobile IP

Action Module cont’d

Action Module cont’d

Action Module cont’d

Action Module cont’d

Action Module cont’d

Undo action Undo per-handoff action How?

MN sends undo message to HA via FAnew. After receiving the message, FA or CN stops copying packets and tunneling them to FAnew, and FAnew cleans its buffer

After that MN communicates with it original network normally When?

The timer in Action Module reaches T0, a constant Whenever starting per-handoff action, the timer starts After handoff action or undo action, the timer stops and is reset to zero

Performance Analysis

Purpose Verify contribution of two-stage scheme Verify contribution of physical layer and MAC layer sensing

Approaches Compare with other mechanisms

Tools The network simulator: NS-2, or Writing a specific simulator using Java or Matlab

Discuss

Limitations Not compatible with Network Address Translation (NAT)

MN behind NAT Gateway allocates a private IP address MN has no routable IP address so it is impossible to establish

a link to HA Not support simultaneous movement

Possibility is very low

Extension to Mobile IPv6 CoAs are co-located, no FA needed Adding an additional server at router to provide data buffer and

forward the buffered packets to MN as the FA in MIPv4

Conclusion

Physical layer and MAC layer sensing decrease latency contributed by detecting new FA and obtaining new CoA

Two-stage mechanism significantly reduces latency by doing some registration work in advance

Multi-tunneling decreases packet loss, and cost due to multi-tunneling can be very low since multi-tunneling lasts very short

Modularization provides a easy implementation Only modification of Mobile IP entities provides high compatibility

and transparency to application The vertical handoff scheme can be applied to real-time application

Selected references

1. Hyosoon Park, Sunghoon Yoon, Taehyoun Kim , Jungshin Park, Misun Do, and

Jaiyong Lee; “Vertical Handoff Procedure and Algorithm between IEEE802.11 WLAN and CDMA Cellular Network”

2. Srikant Sharma Inho Baek Yuvrajsinh Dodia Tzi-cker Chiueh; “OmniCon: A Mobile IP-based Vertical Handoff System for Wireless LAN and GPRS Links”

3. M.Ye, “The mobile IP handoff between hybrid networks”, IEEE, 2002

4. Q. Zhang, C. Guo, Z. Guo, and W. Zhu, “Efficient mobility management for vertical handoff between WWAN and WLAN” IEEE Commun. Mag., vol. 41, pp. 102–108, Nov. 2003

Thanks