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Ask HN: Sim card control frequency?

1 pointsby ParameterOnealmost 8 years ago
Does the sim card control the frequency transmitted? And does the transmitter in the phone allow for a large range of frequencies, like from below 900Mhz up to and past wifi (2.4Ghz)??

3 comments

jepleralmost 8 years ago
I am not a specialist in GSM networking, but I went looking at the relevant standards documents to see whether I could answer your question.<p>It appears that the handset can request information from the SIM about frequency bands. For example, see section 10.3.38 of 3gpp specification #11.11 &quot;Specification of the Subscriber Identity Module - Mobile Equipment (SIM - ME) interface&quot;, which discusses EF_CPBCCH: &quot;CPBCCH storage may reduce the extent of a Mobile Station&#x27;s search of CPBCCH carriers when selecting a cell&quot; <a href="https:&#x2F;&#x2F;portal.3gpp.org&#x2F;desktopmodules&#x2F;Specifications&#x2F;SpecificationDetails.aspx?specificationId=419" rel="nofollow">https:&#x2F;&#x2F;portal.3gpp.org&#x2F;desktopmodules&#x2F;Specifications&#x2F;Specif...</a> [click &#x27;versions&#x27; and then the link &#x27;8.14.0&#x27; to get a zip of a doc file that renders like hell in libreoffice 5 on debian stretch]<p>However, after that I lose myself in random standards document and can&#x27;t give a clearer or more authoritative answer.
sbierwagenalmost 8 years ago
The SIM card doesn&#x27;t contain the radio, the phone itself contains the radio. Phones can only transmit on a fairly narrow set of frequencies, you can&#x27;t tune one to an arbitrary frequency in the gigahertz range.<p>If you want to transmit on an arbitrary frequency you&#x27;ll need to buy a software defined radio, like the HackRF <a href="http:&#x2F;&#x2F;www.kr4.us&#x2F;HackRF-One.html?gclid=CJGdyMDLqtQCFYGUfgodhdkE_A" rel="nofollow">http:&#x2F;&#x2F;www.kr4.us&#x2F;HackRF-One.html?gclid=CJGdyMDLqtQCFYGUfgod...</a>
byoung2almost 8 years ago
It would seem not, since phones (at least in the US) are required to be able to connect to the tower in the absence of a SIM card for 911 calls.
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