1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-04-0098-00-0000.
Title: Handover Scenarios and Use Cases between and
Date Submitted: July, 13, 2004
Presented at IEEE session 3 in City
Authors or Source(s):
  Xiaoyu Liu, Youn-Hee Han
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3. Handover Scenarios and Use Cases between 802.16 and 802.11
Xiaoyu Liu
Youn-Hee Han

4. Contents Background Handover Scenarios and Use Cases
Suggestions and Open Issues

5. Background (1) 802.16 WMAN 802.11 WLAN Infrastructure Technology
Large Coverage
Low Population Density
WLAN
Hot Spot Technology
Moderate Coverage
Dense Aggregations of People and Users

6. Background (2) Integration of 802.16/802.11 Standards
Seamless Handover based on the User Location and Movement
Optimization of Cost, Resources and Performance
Standards
WMAN:
WLAN: a/b/g AP AP AP AP

7. Handover Scenarios (1) Enforced Service Continuity
When one interface is (or will be) disabled, another connection is established to keep session continuity
VHO Events initiated from lower layers: e.g. link down / link going down
H/O Use Cases: 1 & 2 1 1 2

8. Handover Scenarios (2) Policy Driven Selection
The current interface is qualified while other interfaces are available, active session is switched from one interface to another driven by policies or smart decision makers
VHO Events initiated from upper layers: e.g. link switch
H/O Use Cases: 3 & 4 1 3 4

9. Use Cases: Enforced Service Continuity
A user who is using service goes out of the hot spot coverage. The STA detects the degradation of WLAN signal and seamlessly handover the active session from .11 to .16 WMAN without user intervention
A user who is using service goes into blind areas of WMAN coverage where WLAN is deployed. The STA detects the degradation of WMAN signal and seamlessly handover the active session from .16 to 11 without user intervention
Use Case: Fast Mode
A user who is using service drives through or out of the hot spot coverage. Because of the high speed movement and short overlapping distance, a new connection is established with very short latency.
Tight coupling (with L2/L2.5 handover) might be a candidate solution for the fast mode handover between WMAN and WLAN.

10. Use Cases: Policy Driven Selection
A user who is using WMAN service goes into an area covered with several AP and another BS. Some WLAN APs are owned by public WLAN operator, some by company for intranet. When the STA detects the availability of multiple neighbors, the smart decision maker selects the optimal one based on user preferences and a set of policies, then handover the active session from .11 to the optimal interface without user intervention. (Note that link up event might not trigger a VHO immediately)

11. Proposals Technical Requirements (4.1)
Sub-headings below the bullet for handover scenarios between /802.16
Enforced Service Continuity in handover between /802.16
Policy Driven Selection in handover between /802.16

12. Open Issues Open Issues regarding internetworking Models
Loose Coupling
AP and BS Connected via External IP Networks
L3 Handover between and
L3 protocols, e.g. Mobile IP, seems to be a natural solution
Tight Coupling
AP and BS Connected via L2(or L2.5) devices (in the same subnet)
L2 Handover between and (shorter connection re-establishment latency) for Fast Mode cases
Are the .16 and .11 MACs are compatible to be bridged?
Are we going to develop a L2/L2.5 internetworking protocol for / in .21 WG?