1. IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-06-0664-00-0000
Title: QoS considerations in Network Initiated Handovers
Date Submitted: May, 16th, 2006
Presented at IEEE session #14 in Jacksonville
Authors or Source(s):
  Albert Vidal Telemaco Melia Daniel Corujo
Abstract: This document presents the study of network initiated handover scenarios while providing certain QoS to end users and fulfilling operator’s policies.

2. IEEE 802.21 presentation release statements
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The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual < and in Understanding Patent Issues During IEEE Standards Development

3. A network initiated handover study case
Usually, the mobile terminal is assisting the Decision Engine located in the network by providing some information, e.g. signal strength.
In this study, the network decides, because of a change of state in the network, to handover the terminal from one PoA to another
Reasons to handover:
guarantee QoS requirements of user’s applications (data rate, delay, etc.)
follow operator’s policies, e.g. balancing the load among PoAs avoiding congested access networks
Problem:
current draft does not provide the means to perform this kind of handovers
Assumptions:
dual interface mobile device
user is in a overlapping coverage area (PoA1 and PoA2)
mobile device does not assist the handover, all the ‘intelligence’ is in the network

4. 21-06-0664-00-0000 TERMINAL LL MIH HL IF1 IF2 PoA1 PoA2 PoS (MME)
18. MIH_Required_QoS.Res
10. MIH_Configure_Thresholds.Req
TERMINAL LL
MIH HL
IF1
IF2
PoA1
PoA2
PoS (MME)
Old Connection
1. MIH_Required_QoS.Req
11. Link_Configure_Thresholds.Req
12. Link_Configure_Thresholds.Conf
14. MIH_Configure_Thresholds.Req
15. Link_Configure_Thresholds.Req
16. Link_Configure_Thresholds.Conf
13. MIH_Configure_Thresholds.Res
17. MIH_Configure_Thresholds.Res
PoA1 gets overloaded
19. Link_Parameter_Change.Ind
20. MIH_Link_Parameters_Report.Ind
21. MIH_Required_QoS.Ind
Decision Engine decides to HO
2. MIH_QoS_Parameter_Discovery.Req
3. Link_QoS_Parameter_Discovery.Req
4. Link_QoS_Parameter_Discovery.Conf
6. MIH_QoS_Parameter_Discovery.Req
7. Link_QoS_Parameter_Discovery.Req
8. Link_QoS_Parameter_Discovery.Conf
5. MIH_QoS_Parameter_Discovery.Res
9. MIH_QoS_Parameter_Discovery.Res
HO Preparation
HO Initiation

5. 1: QoS Discovery
The Mobility Management Entity (MME) located in the network has to guarantee some QoS requirements of the user. To be able to do it, first it will try to discover what kind of QoS information is available in the PoAs, in this case PoA1 and PoA2. In the first step, the higher layers of the MME, where is located the Decision Engine, send a MIH_Required_QoS.Req (proposed in QoSProposal.doc) to its MIH function.
The MIH in the MME is not aware of what QoS parameters are available from the lower layers of other network entities, so is sending a MIH_QoS_Parameter_Discovery.Req (proposed in QoSProposal.doc) to the PoA2.
The MIH in PoA2 is requesting the QoS parameters available from the lower layers.
The lower layers reply to this request by returning a SupportedQoSParameterList. In our scenario, the list will include the parameter Load.
The MIH function will forward this list to the MME, who requested the information.
Same as 2) for PoA1.
Same as 3) for PoA1.
Same as 4) for PoA1.
Same as 5) for PoA1.
Use of primitives defined in QoSProposal.doc:
MIH_Required_QoS
MIH_QoS_Parameter_Discovery
 Needs to be redefined also as Network to Network
Link_QoS_Parameter_Discovery

6. 2: Configure Thresholds
Now the MME knows what QoS parameters are available at every PoA, so it tries to configure the thresholds, in this case for the maximum Load allowed at the PoA.
MIH function at PoA2 forwards the request to the lower layers.
The lower layers at PoA2 set the requested thresholds and send the response to the MIH function.
The response is forwarded to the originator of the request, the MIH function at the MME.
Same as 10) for PoA1.
Same as 11) for PoA1.
Same as 12) for PoA1.
Same as 13) for PoA1.
The MIH function sends the response of required QoS to the Decision Engine
MIH_Configure_Thresholds
Needs to be redefined also as network  network
Use of QoSParameterList

7. 3: Handover Initiation 21-06-0664-00-0000
Let’s assume that the PoA1, which is still the current PoA of the terminal, receives many new users. The maximum acceptable load threshold previously set will be crossed, which will trigger a Link_Parameter_Change from the lower layers to the MIH function.
This change in the network is reported to the MIH function of the MME
The MIH function will forward to the Decision Engine the change detected in QoS characteristics.

8. Considerations To the current draft:
QoS parameters changes can be triggered also by the network, not only by the terminal.
Possibility to reuse the existing primitives in the draft, with some modifications: the network to network communication is not supported by the primitive MIH_Configure_Thresholds.
To QoSProposal.doc:
Network related parameters can also be the reason to initiate a handover, preventing a QoS degradation at the terminal.
Current terminal related QoS parameters defined in QoSParameterList:
PacketTransferDelay
PacketDelayVariation
PacketLossRatio
PacketErrorRatio
Throughput
New network related parameters suggested:
Current load: use of resources at a network entity, e.g. number of users
Total available bandwidth: actual unused bandwidth, assuming that every user is consuming a different amount of traffic

9. Step forward
How has to proceed to address all QoS-related issues considered in the group?
Option 1:
Merge the different QoS contributions in the group and present a unified proposal  submit a unique modification of the draft.
Option 2:
Keep different QoS contributions separated  submit several modifications of the draft which might be accepted or not independently.

10. References: 21-06-0643-00-0000-QoS_considerations_in_NIHO.doc
QoSProposal.doc
“draft-melia-mobopts-niho-ps-01”, Internet draft on network initiated handovers, Work in progress
“Scalable QoS-Aware Mobility for Future Mobile Operators”, to appear in IEEE Communications Magazine, Special issue on scaling the Mobile Internet, June 2006
Acknowledgements:
The presented contribution has been studied in the framework of the IST collaborative project DAIDALOS ( partially founded by the European commission.