[Ns-developers] Delete a packet in WifiMacQueue

Mirko Banchi mk.banchi at gmail.com
Sun Jan 18 05:24:18 PST 2009


Mathieu Lacage ha scritto:
> On Fri, 2009-01-16 at 12:03 +0100, Mirko Banchi wrote:
>> Hi all,
>>
>> I have to realize aggregation for packets in WifiMacQueue. I have to
>> select all packets that have same receiver address as first packet in
>> the queue and aggregate some of them. If aggregated packet is sent
>> correctly i also have to delete from the queue all packets contained in
>> aggregated packet.
>>
>> Which could be the best way to realize this?
> 
> 
> I think that it is much simpler to avoid this problem:
> 1) when you need to transmit a set of packets, remove them from the
> queue
> 2) keep a copy of the packets in EdcaTxopN after the transmission is
> started to ensure that you can do retransmissions
> 3) drop the copy when the transmission is done.
> 

The problem is:

example:

Packet number - Receiver

WifiMacQueue
--------
 P4-RA
--------
 P3-RA
--------
 P2-RB
--------
 P1-RA
--------

I remove from queue P1 so aggregation could be made with P3 and P4 that
have same receiver RA. But aggregation is performed by an algorithm that
decides how many packets will form aggregated packet so they should be
removed from queue only if they are really part of final A-MSDU.The
others must preserve arrive order.

Another way than deletion with packet id, could be storing of a
PacketQueueI per packet?
Maybe in this way:

std::list<std::pair<Ptr<Packet>,PacketQueueI> >
WifiMacQueue::GetPacketsForReceiver (Mac48Address addr)

and modify

void
WifiMacQueue::Erase (PacketQueueI pos)

Erase is called for every packet in A-MSDU.
If GetPacketsForReceiver is called every time an aggregation occurs the
iterators are always valid.

But in this way code seems too complex :(

regards,
Mirko

-- 
Mirko Banchi

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