Re: [wirelesslan] Reserved bandwidth by AP

Hello Harshal,
I understand that the scheduled TXOP is requested by an QSTA and granted by the AP SME.
In this situation, if the AP SME is not aware of the AP requirement for guaranteed downstream bandwidth, it may think it has sufficient capacity and accept new TS request from QSTA. Once new TS is formed, the AP will protect it by all means and the AP's internally generated traffic will be compromised.
Any comments?
cw

Harshal Chhaya <harshal@gmail.com> wrote:
cw wong wrote:
> 802.11e specify a method to reserve bandwidth through tspec negotiation,
> and this is only initiated by a qsta in qbss.
> In the event that an application (resides in a QAP) needs guaranteed bandwidth for
> its downstream traffic, how can the application obtain this reserved bandwidth with
> its own sme? Please advise.

CW,

Please note that the TSPEC-based reservation is only for the HC (QAP)
to schedule
polls to the QSTA. It is not a true reservation in that other devices
in the network are
not aware of this scheduled traffic.

Under HCCA rules, the QAP can start transmitting a PIFS interval after
the channel is free. This allows it to pre-empt all other QSTAs who
have to wait at least a DIFS before they can start their transmission.

So for any downstream traffic, the QAP can transmit it on its own by
pre-empting all the other QSTAs and ensure that it meets the schedule.
It doesn't need to reserve any resources at the QSTA and so doesn't
need to use TSPECs.

Hope this helps.

Regards,
- Harshal

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