https://qooah.com/2013/08/24/%e7%b6%b2%e7%b5%a1%e9%bb%91%e9%bb%9e%e4%b8%80%e7%9b%ae%e4%ba%86%e7%84%b6%e3%80%8aopensignal-3g-4g-%e7%84%a1%e7%b7%9a%e5%9c%b0%e5%9c%96%e3%80%8b%e5%9f%ba%e7%ab%99%e5%b0%b1%e5%9c%a8%e8%ba%ab%e9%82%8a/