1. Enhancing BSS Transition Management
May 2009
doc.: IEEE /1294r2
May 2009
Enhancing BSS Transition Management
Date:
Authors:
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

2. May 2009
doc.: IEEE /1294r2
May 2009
Abstract
Amendment proposals (on IEEE802.11v) are made to enable a streamlined network-initiated BSS transition process indication when the current AP cannot honor more resource (TSPEC) requests, while neighboring APs have abundant unused radio resource.
The resulting network-initiated load shifting indication process is more effective, efficient and deterministic in enabling an STA-initiated BSS transition process.
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

3. May 2009
doc.: IEEE /1294r2
May 2009
Overview
Issues with current BSS transition indication to an STA after TSPEC rejection
Proposed solution to provide BSS transition indication to STAs after TSPEC rejection
Standard amendment proposal
Straw polls
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

4. Consequence of STA operations after TSPEC rejection
May 2009
doc.: IEEE /1294r2
May 2009
Consequence of STA operations after TSPEC rejection
If the ADDTS Request is rejected, the mobile STA doesn't know its full range of possible next steps.
Currently, the mobile STA can:
retry with new TSPEC settings,
transition to another AP based on its own logic,
issue a BSS transition query to the current AP,
reject the session, or
Wait.
Each of these alternatives involves a multistep sequence which could fail, require successive attempts or result in delays in obtaining the desired traffic service.
Adding a status code to suggest load shifting would make a deterministic and efficient indication for the STA to start a BSS transition
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

5. STA-initiated operations due to TSPEC Rejection
May 2009
doc.: IEEE /1294r2
May 2009
STA-initiated operations due to TSPEC Rejection
STA
Associated AP
ADDTS Request (TSPEC)
There is no existing status code to indicate the opportunity of BSS transition.
A status code to indicate the opportunity for BSS transition is critical to enable the STA with the best next step
ADDTS Response
(?status code)
1. SUCCESS
2. INVALID_PARAMETERS
3. REJECTED_SUGGESTED_CHANGES (TSPEC)
4. REJECTED_FOR_DELAY_PERIOD
5.REJECTED_WITH_SUGGESTED_BSS_TRANSITION (Proposed Status Code)
STA possible actions after TSPEC rejection:
Try new TSPEC settings
Try another AP
Request a BSS transition
Reject Session
Wait
When the TS request is rejected, the handset doesn't know its full range of possible next steps. Currently it can retry with new Tspec settings, retry another AP based on its own logic, request a BSS transition, reject the session or wait. The option to choose BSS transition is missing
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

6. Standard Amendment Proposal
May 2009
doc.: IEEE /1294r2
May 2009
Standard Amendment Proposal
Add the new status code REJECTED_WITH_SUGGESTED_BSS_TRANSITION, to be optionally used by an AP within an ADDTS Response frame.
If an AP rejects a TSPEC request and is aware of alternative candidate APs that can meet the request and the non-AP STA supports the BSS Transition capability, the AP can set the status code to REJECTED_WITH_SUGGESTED_BSS_TRANSITION .
A non-AP STA receiving such a message immediately starts the BSS transition process.
Affected clauses:
Status Code field
MLME-ADDTS.confirm
MLME-ADDTS.response
TS Setup
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

7. 802.11v BSS Transition Management Indication due to TSPEC rejection
May 2009
doc.: IEEE /1294r2
May 2009
802.11v BSS Transition Management Indication due to TSPEC rejection
Current AP
STA
ADDTS Response ( STATUS CODE = REJECTED_WITH_SUGGESTED_BSS_TRANSITION )
Indicate to the STA the availability of resources within neighboring APs
BSS Transition Query (Reason Code )
BSS Transition Request (Neighbor Report element)
BSS Transition Response (status code, target BSSID)
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

8. May 2009
doc.: IEEE /1294r2
May 2009
Proposal to add BSS transition indication status code with TSPEC response
SUCCESS 38
INVALID_PARAMETERS
The request has not been successful as one or more parameters have invalid values 39
REJECTED_WITH_SUGGESTED CHANGES
The TS has not been created because the request cannot be honored; however, a suggested TSPEC is provided so that the initiating STA may attempt to set another TS with the suggested changes to the TSPEC 47
REJECTED_FOR_DELAY_PERIOD
The TS has not been created; however, the HC may be capable of creating a TS, in response to a request, after the time indicated in the TS Delay element.
New status code
REJECTED_WITH_SUGGESTED_BSS_TRANSITION
The TS has not been created because the request cannot be honoured; however, the HC suggests the STA to transition to other BSSs to setup the TS.
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

9. May 2009
doc.: IEEE /1294r2
May 2009
Summary
Proposal to streamline network-initiated BSS transition (load shifting) indication by coupling the TS setup process to the BSS transition process using a designated status code.
A STA becomes aware of all opportunities when a TSPEC request is denied. The process to transition becomes more efficient and deterministic, should the STA decide to transition to another AP
The solution requires only the addition of a status code, providing STA with valuable information.
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

10. References IEEE Std. 802.11-2007 IEEE 802.11v D4.01, January 2009
May 2009
doc.: IEEE /1294r2
May 2009
References
IEEE Std
IEEE v D4.01, January 2009
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks

11. May 2009
doc.: IEEE /1294r2
May 2009
Straw Poll Questions
Do you agree that a TSPEC response with a status code suggesting a BSS transition should be included in the new revision of the v draft?
Yes: No: Abstain:
Guyves Achtari, Nortel Networks
Guyves Achtari, Nortel Networks