Enabling Hybrid Coordinator Mobility. John Kowalski Sharp Labs of America November 2001. Why We Need a Mobile HC. Wireless AV applications need Guaranteed Services (meeting objectives for data rate delivery, delay and jitter).
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Enabling Hybrid Coordinator Mobility
Sharp Labs of America
1. STA associates with (E)AP (may or may not be enhanced access point).
2. IF STA wishes to be HC (or needs Hybrid Coordinator) then
2.1 STA makes query to the Access Point (Request HC Candidacy message,
2.2 STA gets response from (E)AP (“HC ”) indicating: who if anyone is the HC.
2.3 IF a new HC is chosen, the AP broadcasts that by new HC Status message- new HC is always first in the HC list (see text) The HC status message also includes the QoS state: the list of STAs and TSPECs that define the QoS flows.
3. Stations then renew their “registration” of streams (if they previously have been granted TSPECs for streams), or initiate new TSPEC negotiation with the new HC, and thereby create a new registration with the HC.
1. HC sends Request HC Resignation message
2. AP sends HC Status message.
3. If another STA is in the candidate list, the AP probes the highest candidate on the candidate list, to determine if that STA is still HC-capable. If so, the AP broadcasts the new AP and the procedure of steps 2.3 and 3 of the Establishment process are followed.
4. IF another STA wishes to be HC (or needs Hybrid Coordinator) then
the procedure from step 2 on of HC Establishment is followed.
5. If there NO STAs that are candidates for HC or have requested to become HC, polled QoS service is discontinued, and streams are terminated.
Station Assuming Role of AP/HC
1. Through broadcast messages (originating from above the MAC), BSSID’s are broadcast of potential APs.
Stations keep a table of potential APs to associate with in the even they are no longer to communicate with the current AP (which may happen because the STA has moved out of range of the AP for example.) These may be broadcast from the PAL.
When interference becomes great enough, or when a predetermined number of beacons are not detected then:
2. A station wishing to become an AP/HC issues a DISSOCIATION message to the AP it was associated with, and dissociates from the BSS.
3. A station wishing to become an AP/HC issues an Mac Layer Management Entity START (MLME-STARt.request) primitive, instantiating a BSS with itself as AP.