[Tinyos-help] about 802.15.4 ack

[Razvan Musaloiu-E.]

Hi!

On Tue, 28 Apr 2009, 林枫 wrote:

> Hi,Razvan ME:
>      Thank you for you reply.I have read the file CC2420PacketC.nc, but i
> can not find any code that handles this problem.In 802.15.4-2006,there is no
> content to
> handle this problem too.I have read some implementation of 15.4 written in
> c,they just ingore this problem and let the upper layer to handle the
> duplicate frame(maybe process it once more ).I wonder why they do not handle
> this problem in the mac layer.I mean i can keep a table in the mac layer to
> record the sequence number of different source node , if the sequence number
> of the incoming frame is the same as the sequence number of last frame from
> the source node,we discard it.Maybe it costs too much,but if we do not do
> anything  there will be errors.

One more place to look at is this one:
 	tinyos-2.x/tos/chips/cc2420/unique

The table that keeps track of the sequence numbers is in 
UniqueReceiveP.nc. :-)

--
Razvan ME

> 2009/4/28, Razvan Musaloiu-E. <razvanm at cs.jhu.edu>:
>>
>> Hi!
>>
>> On Tue, 28 Apr 2009, 6lowpan wrote:
>>
>>  Hi everyone.
>>>
>>> In 802.15.4,when a receiver receives a frame from a sender ,it will send
>>> back an ack.If the sender fails to receiver the ack,it will send the frame
>>> with the same sequence number again.
>>>
>>
>> The retransmission happens only if the PACKET_LINK is enabled.
>>
>>  I can not find how the receiver handles this frame in the document.Does it
>>> discard it or process it once more?
>>>
>>
>> The code is in tinyos-2.x/tos/chips/cc2420/packet.
>>
>> All the best!
>> Razvan ME
>>
>