Mobility management and power management are two essential functions in a wireless system. For a wireless device to be reached at any time or location, there is a need for the wireless device to support a low rate connection while not actively engaged in a voice call or data session. Mobility management involves messaging between the wireless device and the radio access network (RAN) related to connection management functions, for example, location, paging, cell reselection, and handoff.
Effective power management is essential to conserve battery power. Power saving modes in a wireless device, such as idle mode or sleep mode, decrease the wireless device functions to a minimum so as to maintain some connectivity to the network while conserving power. Each radio access technology (RAT) standard stipulates its own mobility and power management functions. To perform mobility and power management efficiently, wireless standards have introduced state machines at the network layer and/or at the Media Access Control (MAC) layer.
Modern wireless devices, such as smartphones, netbooks, tablets can operate in heterogeneous network regions comprising network nodes supporting different RATs, e.g., GSM/EDGE/3G base stations, WiFi Access Points). Most wireless devices are capable of multi-mode operation (e.g., GSM/EDGE/3G/WiFi/Bluetooth/NFC), i.e., there are multiple radios in a wireless device capable of simultaneously accessing different Radio Access Networks (RANs) with each RAN supporting one or more RATs.
Future wireless device configurations will include even more modes of radio operation including future technologies such as LTE-Advanced as well as sensor radios and cognitive radios. In a multi-mode wireless device, radios that are not actively transmitting (e.g., in IDLE mode) use up some bandwidth and power for state management functions. The battery power usage increases with more radios in a wireless device, even if they are in their lowest power operating state. Further, placing radios in their lowest power operating state results in potential delays when the wireless device has to respond to an incoming voice call or data session. Therefore, there is a need for efficient low power operation modes for a multi-radio wireless device, such as the systems and methods discussed below in the present disclosure.