how to find 3g modem signal strength with out AT commands?

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http://www.linuxquestions.org – when i try to find signal strength of my modem using AT+CSQ, the usb device is locked by the network manager. To find the signal strength with AT+CSQ i have to first disable network connection using #nmcli nm wwan off to unlock the device inode /dev/ttyUSBX. Is there any nmcli option to get signal strength or any other option? The gdbus object for NetworkManager don't have any method like getSignalStrength. nm-applet was able to display signal strength in system tray. so there should be a way to get signal strength form network manager! (HowTos)