The modem has a number of states it can be resident in as it operates in conjunction with the host application and the network infrastructure. When the modem powers up it passes quickly through its initialization routines and either enters the idle or receive mode.
Off Mode (no Supply)
No power is supplied to the modem either through the supply connections or inadvertently through the signal lines and protection diodes.
Off Mode (Supply connected but not active)
A compliant supply voltage is supplied to the modem through the supply connections and the signal lines, especially the wake-up line, are at the low state. The leakage current in this mode is less than 100 micro-amps.
Idle Mode
The idle mode is active when the modem is directed to disconnect (de-register) from the network or not to initiate the registration process. The modem will accept AT commands and act accordingly. If directed to connect to an IP, the modem can automatically begin the registration process and subsequently connect to the destination. The idle mode consumes approximately 60 milli-amps.
Network Maintenance
Certain messages are required to be sent by the modem in order to start, maintain or end a network connection. These include the registration process, coordinated channel hops, registration maintenance and channel selection.
Receive Mode
Receiving signals from the network, the modem will activate the receiver circuits whenever the unit is awake and registered on the network. The modem must accurately track the incoming RF signal to ensure that the modem is focused on the strongest accessible channel. It must also determine the incoming signal strength so that it can adjust it’s transmit signal strength. The receive mode consumes approximately 95 milli-amps.
Transmit Mode
Transmitting signals to the network, the modem will activate its transmitter circuits whenever the unit is awake, needs to send data and is registered on the network. The modem also needs to transmit Network Maintenance messages to remain connected and to coordinate channel communications. The transmit power level is determined by the receive signal strength and the Power-product setting contained in the forward channel data stream. The modem automatically compensates for the varying distance between itself and the base station. This arrangement is very effective at overcoming the near/far problem associated with a wide area wireless network. The transmit mode consumes approximately
800 milli-amps for power level 2.
600 milli-amps for power level 3.
400 milli-amps for power level 4.
300 milli-amps for power level 5.
250 milli-amps for power level 6.
200 milli-amps for power level 7.