[Hilo] Why BER information of <AT+CSQ> not be detected?

[Hilo] Why BER information of <AT+CSQ> cannot be detected? I see only 99 returned.

Answer: The <AT+CSQ> can return RSSI and BER value also.
RSSI is a measurement done on the control channel.
BER is a measurement done on the data channel.
BER can only be detected and valid when a voice call is active. Or 99 will always be returned when no voice call ongoing.