Quick overview of what's here:* benchmark_tx.py: generates packets of the size youspecify and sends them across the air using the USRP.  Known to workwell using the USRP with the RFX transceiver daughterboards.You can specify the bitrate to use with the -r <bitrate> command lineparameter.  The default is 500k.  Some machines will do 1M or more.You can select the modulation to use with the -m <modulation> commandline argument.  The legal values for <modulation> are gmsk, dbpsk and dqpsk.* benchmark_rx.py: the receiver half of benchmark_tx.py.Command line arguments are pretty much the same as rx.  Works wellwith a USRP and RFX transceiver daughterboards.  Will also workwith TVRX daugherboard, but you'll need to fiddle with the gain.  Seebelow.  Prints a summary of each packet received and keeps a runningtotal of packets received, and how many of them were error free.There are two levels of error reporting going on.  If the access code(PN code) and header of a packet were properly detected, then you'llget an output line.  If the CRC32 of the payload was correct you get"ok = True", else "ok = False".  The "pktno" is extracted from thereceived packet.  If there are skipped numbers, you're missing somepackets.  Be sure you've got a suitable antenna connected to the TX/RXport on each board.  For the RFX-400, "70 cm" / 420 MHz antennas for hamhandi-talkies work great.  These are available at ham radio supplies,etc.  The boards need to be at least 3m apart.  You can also tryexperimenting with the rx gain (-g <gain> command line option).Generally speaking, I start the rx first on one machine, and then fireup the tx on the other machine.  The tx also supports a discontinoustransmission mode where it sends bursts of 5 packets and then waits 1second.  This is useful for ensuring that all the receiver controlloops lock up fast enough.* tunnel.py: This program provides a framework for building your ownMACs.  It creates a "TAP" interface in the kernel, typically gr0,and sends and receives ethernet frames through it.  See/usr/src/linux/Documentation/networking/tuntap.txt and/or Google for"universal tun tap".  The Linux 2.6 kernel includes the tun module, youdon't have to build it.  You may have to "modprobe tun" if it's notloaded by default.  If /dev/net/tun doesn't exist, try "modprobe tun".To run this program you'll need to be root or running with theappropriate capability to open the tun interface.  You'll need to fireup two copies on different machines.  Once each is running you'll needto ifconfig the gr0 interface to set the IP address.This will allow two machines to talk, but anything beyond the twomachines depends on your networking setup.  Left as an exercise...On machine A:  $ su  # ./tunnel.py --freq 423.0M --bitrate 500k  # # in another window on A, also as root...  # ifconfig gr0 192.168.200.1On machine B:  $ su  # ./tunnel.py --freq 423.0M --bitrate 500k  # # in another window on B, also as root...  # ifconfig gr0 192.168.200.2Now, on machine A you shold be able to ping machine B:  $ ping 192.168.200.2and you should see some output for each packet in thetunnel.py window if you used the -v option.Likewise, on machine B:  $ ping 192.168.200.1This now uses a carrier sense MAC, so you should be able to sshbetween the machines, web browse, etc.* run_length.py: This program takes a single argument '-f FILE' andoutputs the number of runs of similar bits within the file. It isuseful as a diagnostic tool when experimenting with line coding orwhitening algorithms.