CELLULAR_REGISTRATION_NOT_REGISTERED: The modem is not registered with any network. 
This can occur when the modem is either turned on but has not yet attempted to connect, 
or it has lost its registration with any available networks.

CELLULAR_REGISTRATION_REGISTERED_HOME: The modem is registered with its home network. 
This means the modem is connected to the network of the operator with which the SIM card is associated, 
and normal cellular service is available.

CELLULAR_REGISTRATION_SEARCHING: The modem is actively searching for a network to register with. 
This is usually seen when the modem is trying to find a suitable network in its area 
but hasn't yet connected.

CELLULAR_REGISTRATION_DENIED: The modem's registration attempt has been denied by the network. 
This can happen for various reasons, such as an invalid SIM card, network restrictions, 
or account issues with the mobile operator.

CELLULAR_REGISTRATION_UNKNOWN: The modem's registration status is unknown. 
This status typically indicates that the modem is unable to determine its current registration state, 
which might be due to internal errors or communication issues.

CELLULAR_REGISTRATION_REGISTERED_ROAMING: The modem is registered with a roaming network. 
This means the modem is connected to a network that is different from the home operator's network, 
typically used when the device is outside its normal geographical area and is using a partner network.