get carrier name and signal strength return wrong value in iphone

Question

i curious why i get wrong value to get carrier name and signal strength. Here the code.

CTTelephonyNetworkInfo *netinfo = [[CTTelephonyNetworkInfo alloc] in         


        

Answer 1

It is quite common that signal strength values are returned as integer numbers. The tricky point is the mapping to the corresponding dBm value. Usually the int values provide a resolution of 0.5, 1, or 2 dBm. The dBm values reported by the handset/modem usually range from -115 to -51 dBm for 2G (GSM/EDGE) and -120 to -25 dBm for 3G (UMTS/HSxPA) and represent the RSSI (received signal strength indicator).

E.g. the Android API uses the default 3GPP mapping (see Android reference).

Please take also into account that the baseband modem differs between the iPhone 4S (Qualcomm) and earlier models which used an Infineon Gold.

Answer 2

About the carrier: Running your code on the simulator gives me nil while running on a device correctly says 2011-11-24 10:49:05.182 testapp[12579:707] Carrier Name: Vodafone.de, so the code is absolutely correct (running on iOS 5.0.1 using Xcode 4.2). Maybe your carrier didn't fill out some field correctly? In any case I would consider testing on another device or with another SIM card.

Concerning signal strength: As CTGetSignalStrength seems to be a rather undocumented API the values may be arbitrarily defined by Apple (and redefined as well). In any case this seems to be a RSSI value (received signal strength indication) which is more or less a positive number where 1 is the worst signal strength and upper is better. As such there is no predefined (documented and thus stable) available mapping to dBm values, a mapping would probably have to be created experimentally.