Re: [Discuss-gnuradio] benchmark_ofdm with -s 16

[Hoo-chang Shin]

Hi Tom, 

but as far as I see from the code, only max. 16 subcarriers are handled for a 
IFFT.
That is to say:

Tx-chain:
16 byte data -> CRC -> make packet -> mapper_bcv -> insert preamble -> IFFT -> 
cyclic prefix

And when the size of the data exceeds 16, say 17, then anonther Tx-chain goes 
through for the 1 byte.

So I thought, with the option -s 16 I'm sending the 'basic' size of the each Tx 
elements.

And when the receiver side does not detect all right, the reason may be that 
the transceiving happens too fast?

Hoo Chang.


----- Original Message ----
From: "address@hidden" <address@hidden>
To: Hoo-chang Shin <address@hidden>
Cc: address@hidden
Sent: Friday, June 20, 2008 3:09:00 PM
Subject: Re: [Discuss-gnuradio] benchmark_ofdm with -s 16

> ---------------
> Hi,
>
> when I send from the 'benchmark_ofdm_tx.py' with option -s 16, then about 200
> of the packets in the end are lost at the receiver side.
> Might it be a problem at the code, or am I doing anything wrong or missing
> something?
>
> These are the command I used:
> .../benchmark_ofdm_tx.py -T A -f 2.45G -i 512 -M 0.04 -s 16
>  (Then it transmits 2500 packets each of size 16)
>
> .../benchmark_ofdm_rx.py -R A -f 2.45G -d 256
>  (Then I get about 2300 to 2480 packets received at the receiver side)
>
>
> More insteresting:
> when I send the pre-saved data, which is saved from the
> 'benchmark_ofdm_tx.py',
> direct to the USRP, then about 150 to 200 packets are lost
> - that is:
> I get about 2300 to 2370 packets received at the receiver side.


16 subcarriers is a really small number to use and it's likely not being picked
up by the receiver.

Tom