A basic USRP2 + BBN receiver + Samples_per_symbol question + An observation

Hello list,
I have been fiddling around with USRP2 version of BBN code for a week
now.
First, one observation I found is: if and only if I set decimation to 4
(i.e., 25Msps), I see almost all of the 1Mbps packets sent by my 802.11
sender. This includes data packets (1400 bytes payload), and
IEEE802.11 association/reassociation request packets. I wonder why?

My Specification:

My setup:

  • Infrastructure mode
  • AP has a fixed data rate set to 1Mbps so that BBN code receives
    ALMOST
    all the packets

Now, onto my MAIN question:

  • If the sender at 1Mbps is using DSSS (Barker code), and I am
    receiving
    with decimation factor 4 using USRP2,
    • How many samples per symbol should I expect (I am assuming 1 symbol
      per
      bit, thus samples per symbol = samples per bit)? I collect samples
      using
      usrp2_rx_cfile.py [rx-file=b.dat] and analyze in Matlab.
    • So, 25MSps (complex float symbol) sampling rate, how many samples
      per
      bit ought I expect. I do b = read_complex_binary(‘b.dat’) in matlab ,
      and
      look at plot(abs(b))?

Thank you in advance for your time.