The multitude of incompatible mobile phone systems in the United States and some other countries makes the situation more difficult—it is not clear if the onboard repeaters will be compatible with all of the different cell-phone protocols (TDMA, GSM, CDMA, iDen) and their respective providers.
在美国和其他一些国家的多种不兼容的移动电话系统使情况更加困难——这是不明确的，如果内置中继器兼容所有不同的手机协议（TDMA，GSM，CDMA，iDen）及它们各自的供应商。