[Ns-developers] 802.11e/n Block Ack implementation status

[Mirko Banchi]

Il giorno 12/lug/09, alle ore 15:46, Basim Javed ha scritto:

> hi
> let me quote one line from standard 802.11: "A fragment is an MPDU,  
> the payload of which carries all or a portion of an MSDU or MMPDU."

I repeat:

Term MSDU is used to indicate the packet not fragmented like it is  
forwarded down from LLC Layer.
All unit that are transmitted we could call them MPDUs. So a MSDU  
fragment is an MPDU, a MSDU not fragmented is a MPDU, and a A-MSDU is  
a MPDU.


> Basic variant: so it means 2 bytes per MPDU/MSDU are used in the  
> bitmap of total size 128 bytes; hence maximum 64 MPDU/MSDU can be  
> acknowledged in one bit map.
> ALSO: each MPDU/MSDU can have 16 fragments, as there are 16 bits for  
> it, or what? Suppose an MPDU/MSDU has 11 fragments, then 11 bits are  
> used, and remaining 5 bits are not used, but that MPDU/MSDU will  
> consume 16 bits in the bitmap?
>

Yes. If you use basic variant and if you send no fragmented MSDU only  
one bit is used.

> TXOP: suppose a block has 20 MPDU/MSDU, and suppose a TXOP sends  
> only 4 of them each time: it means that it will take 5 TXOP to send  
> the complete block, followed by the blockackreq, and then finally  
> blockack frame coming from the receiver?
>

It depends on length of packets and on length of TXOP. If all packets  
are equals long. Yes

> LAST: how many MPDU/MSDU are typically sent in one block, and I  
> guess each MPDU/MSDU can be of max size 2304 bytes (or maybe 1500  
> bytes for WLANs)?
>

With compressed variant also exchange of A-MSDU under block ack is  
permitted so max length permitted is max lentgh of an A-MSDU  
(typically 7935 bytes)

The standard doesn't specify if with basic variant is permitted use of  
A-MSDU.

Regards,
Mirko

--
Mirko Banchi

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