[Discuss-gnuradio] USRP2 high data throughout for WiFi 802.11 processing or GALILEO E5

[Fabrizio Tappero]

Hello guys,
I suppose some people out there are interested, like me, in doing
stuff with relatively large-bandwidth signals like 20MHz WiFi stuff or
even 50 MHz GALILEO E5.
on a linux ubuntu 10.04, USRP2/XCVR2450, GNURadio 3.2 (I think) with
two week old FPGA firmware, I am trying to collect some data file with
the command:
sudo usrp2_rx_cfile.py -v -s -e eth1 -f 2462.0M -g 25 -d 5 -N 250M wifi_d5.bin

and (with a WBX front end) also this:
sudo usrp2_rx_cfile.py -v -e eth1 -f 1575.42M -s -g 25 -d 14 -N 700M
galileoE1.bin

1) I however do not seem to set the decimation d=4, for the XCVR2450
front end. Is it a firmware problem? Does anybody knows why?

2) Regarding the USRP 2 bandwidth, digging into the GNU Radio forum I
found people confirming this:

In (USRP2) RX path:
if ADC sampling = 100MHz,
and if Min decimation = 4
=> max IF bandwidth = 25MHz
=> Max IF Ethernet rate = 4 bytes per sample * 25 MSPS = 100 Mbyte/sec
= 800 Mbit/sec (Every thing is clear)

My question is: with a decimation of 4 you get a fs = 25MHz and
therefore I would think that the bandwidth that you can capture is
actually half that, meaning ~12MHz. Could somebody explain to me why I
am wrong?

Thank you in advance for your attention
Regards,
Fabrizio