A client device including a wireless network access device (30, 130) that is adapted to receive messages over a communication channel, the wireless network access device (30, 130) having a powered state and a power-off state, the client device comprising: a programmable timer for allowing operation of the wireless network access device (30,130) in the powered state; and a controller that is adapted to be in communication with the programmable timer and capable of providing a time period during which the wireless network access device (30, 130) is operated in the powered state, the controller being adapted to determine the time period based at least on a given value of a discontinuous reception parameter obtained by the wireless network access device (30, 130) from a wireless network such that, when the discontinuous-reception parameter specifies a greater frequency interval for checking paging messages, the time period for switching the wireless network-access device to the power-off state is reduced, and, when the discontinuous-reception parameter specifies a lesser frequency interval for checking paging messages, the time period for switching the wireless network access device to the power-off state is increased; wherein the client device is adapted to be embedded in a vehicle; characterized in that it comprises means to determine the time period for operating the wireless network access device after the controller determines that an ignition system of the vehicle has been shut-off; the wireless network access device is able to operate at a lower voltage level than normal, and the controller is adapted to determine the time period for operating the wireless network access device in a powered state additionally based on the wireless network access device operating at the lower voltage level than normal. a programmable timer for allowing operation of the wireless network access device (30,130) in the powered state; and a controller that is adapted to be in communication with the programmable timer and capable of providing a time period during which the wireless network access device (30, 130) is operated in the powered state, the controller being adapted to determine the time period based at least on a given value of a discontinuous reception parameter obtained by the wireless network access device (30, 130) from a wireless network such that, when the discontinuous-reception parameter specifies a greater frequency interval for checking paging messages, the time period for switching the wireless network-access device to the power-off state is reduced, and, when the discontinuous-reception parameter specifies a lesser frequency interval for checking paging messages, the time period for switching the wireless network access device to the power-off state is increased; wherein the client device is adapted to be embedded in a vehicle; characterized in that it comprises means to determine the time period for operating the wireless network access device after the controller determines that an ignition system of the vehicle has been shut-off; the wireless network access device is able to operate at a lower voltage level than normal, and the controller is adapted to determine the time period for operating the wireless network access device in a powered state additionally based on the wireless network access device operating at the lower voltage level than normal.