= Frequently Asked Questions =

A series of questions commonly asked (and answered). Gathered from the mailing list archives and various experts.

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General
Who/what/when/where/why types of questions and links to different areas.

=== What is GNU Radio? ===
GNU Radio is a collection of software that when combined with minimal hardware, allows the construction of radios where the actual waveforms transmitted and received are defined by software. What this means is that the digital modulation schemes used in today's high performance wireless devices are now software problems.

=== Where can I download GNU Radio? ===
Check the [wiki:Download Download] page on the wiki!

USRP
Questions specific to the USRP, it's functionality, using it with multiple antennas, multiple USRPs on the same host, daughterboards, etc, etc.

=== Can multiple USRPs be installed on one single host? ===
Yes. This is done using the {{{which}}} parameter in the {{{usrp.source_c()}}} and {{{usrp.sink_c()}}} method as shown below: {{{
src1 = usrp.source_c( which=0 )
src2 = usrp.source_c( which=1 )
}}}

Now which USRP gets assigned #0 and #1 is dependent on the order they
enumerate on the USB, first by bus, then by device. This may be
affected by which one is plugged in first or turned on first.

It's possible, when writing your own code, to retrieve the serial number
from the {{{source_c}}} object and use that to determine which actual hardware
unit you've grabbed.

The other caveat is that most motherboards share a single USB controller
for all their ports. So you're sharing the same 32 MB/s bandwidth
across two USRPs now, effectively halving the maximum RF bandwidth you
can work with if both USRPs are using the USB equally.

=== Can I run 802.11a/b/g/n/? with a USRP? ===
An answer here.

=== What frequency ranges are covered that I can use with the USRP? ===
Links to the various daughterboards and their frequency ranges.

=== Can I transmit and receive from the same USRP? ===
Answer here.

Core Processing
Different waveforms that are developed and working. Links to works in progress. Explaining Python, C++, etc.

=== Do you support BPSK/D-BPSK/QPSK/M-QAM/OFDM/etc. ===
Sure here are some examples. The information can be found here. If it hasn't been implemented, try it yourself! You'll be surprised what you'll learn.

=== What are the building blocks of GNU Radio at my disposal? ===
Link to doxygen classes or examples.

=== Why bother with Python? I just want to code in C++! ===
It's being worked on. Point to ticket.

=== Isn't Python slow? My application requires blazing speed. ===
Python is only used to setup the flow graph. Once setup, most of the work is done in C++.

Implementing your own C++ Block
Information about using SWIG between C++/Python specifically for GNU Radio.

=== How do I write a block? ===
Read the tutorial on how to write a block.