<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>cnvogel</author><text>There are currently (to my knowledge) two working open-source/free-software implementations of the GSM stack.&lt;p&gt;OpenBTS (&lt;a href=&quot;http://openbts.sourceforge.net/&quot; rel=&quot;nofollow&quot;&gt;http://openbts.sourceforge.net/&lt;/a&gt;) puts everything, beginning at the modulation/demodulation of the radio-frequency, into your PC and uses a USRP (&lt;a href=&quot;http://www.ettus.com/products&quot; rel=&quot;nofollow&quot;&gt;http://www.ettus.com/products&lt;/a&gt;) as the radio-frequency frontend (~$2000).&lt;p&gt;OpenBSC (&lt;a href=&quot;http://openbsc.gnumonks.org&quot; rel=&quot;nofollow&quot;&gt;http://openbsc.gnumonks.org&lt;/a&gt;) uses a different approach and starts implementing at the Abis-interface, which is what the Base Transceiver Station (the thing with the antennae...) connects to. Here you don&apos;t need the USRP but a surplus GSM BTS (currently around or a little less than $500/€500 and the necessary E1-interface (for the Abis-link) is $200/€200, afaik). OpenBSC has been successfully tested at &lt;a href=&quot;https://wiki.har2009.org/page/GSM&quot; rel=&quot;nofollow&quot;&gt;https://wiki.har2009.org/page/GSM&lt;/a&gt; and &lt;a href=&quot;http://events.ccc.de/congress/2009/wiki/GSM&quot; rel=&quot;nofollow&quot;&gt;http://events.ccc.de/congress/2009/wiki/GSM&lt;/a&gt; using officially allocated frequencies.</text><parent_chain></parent_chain></comment><story><title>OpenBTS: Cheap, open source cellular network</title><url>http://openbts.sourceforge.net/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>vaporstun</author><text>Looks very cool, excited about the possibilities, but my first thought was &quot;FCC violation.&quot;&lt;p&gt;Did a quick Google search, looks like they did a test at Burning Man in 2008 and got local FCC approvals: &lt;a href=&quot;http://lwn.net/Articles/297038/&quot; rel=&quot;nofollow&quot;&gt;http://lwn.net/Articles/297038/&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>OpenBTS: Cheap, open source cellular network</title><url>http://openbts.sourceforge.net/</url></story>