Selective scanning for legacy radio coverage in idle mode

A mobile device may implement an idle mode process in order to selectively scan for legacy radio coverage using a timer-based scanning process. A mobile device may operate in idle mode and may establish a long term evolution (LTE) radio link with a nearby cell site. The idle mode process implemented by the mobile device may include evaluating one or more criteria that are indicative of whether the mobile device is capable of providing sufficient voice service capabilities using voice over LTE (VoLTE). Based on the criteria evaluation, a timer-based scanning process may be initiated. When the timer-based scanning process is initiated, the mobile device may scan for legacy radio coverage periodically. If no legacy radio coverage is available, the mobile device may indicate that voice services are unavailable.

BACKGROUND

Cellular networks are constantly evolving. For example, fourth generation (4G) Long Term Evolution (LTE) networks have evolved from third generation (3G), and second generation (2G) radio access technology (RAT) systems. The 3rdGeneration Partnership Project (3GPP) LTE standard, in its various releases, is an all-Internet Protocol (all-IP) data transport technology that uses packet-switching for both data and voice communications. By contrast, legacy RAT systems (e.g., 3G/2G) employ circuit-switching for voice communications. Because the evolution of these technologies takes time, cellular networks employ a mixture of newer (e.g., 4G) and legacy (e.g., 3G/2G) RAT systems. Such networks can be thought of as “heterogeneous” cellular networks due to the mixture of legacy and non-legacy technologies.

Mobile devices that are 4G LTE-compliant are configured to communicate within these heterogeneous cellular networks by employing radios that can communicate through the legacy RATs. Generally, 4G LTE-compliant mobile devices are configured to prefer attachment to 4G LTE networks, which offer relatively high data-rate throughput as compared to the legacy radio access networks (RANs). In most mobile devices, a choice of which protocol to employ depends primarily on what RATs are available to the mobile device at its present geographic location. Furthermore, in instances where the preferred 4G LTE RAT is unavailable or unusable, legacy RATs, if available, may be used as a fallback protocol, such as by using a circuit-switch fallback (CSFB) mechanism.

However, with the availability of additional spectrum (e.g., the 700 megahertz (MHz) Band), LTE-based RATs are able to attain better link budget and coverage as compared to legacy RATs due to improved propagation characteristics in the new spectrum. For example, given a single cell site (cell tower), a 700 MHz LTE footprint (i.e., LTE radio coverage area) tends to be larger than the legacy 3G/2G footprint for the same cell site. Without a commensurate enlargement of the legacy 3G/2G footprint, this creates “LTE-only” radio coverage areas (sometimes called “LTE-only areas”) where the only available RAT available to the mobile device is the 4G LTE RAT.

When a mobile device is within an LTE-only area, the only way to deliver voice is through a packet-based protocol, such as the voice over LTE (VoLTE) protocol. Accordingly, an LTE-compliant mobile device within an LTE-only area generally indicates that voice service is available on the assumption that VoLTE can be used for voice communications. However, VoLTE may not always be available or usable in LTE-only areas. Consider an example where a mobile device attempts to establish a call over VoLTE in an LTE-only area and a failure occurs that prevents the use of VoLTE for the call, such as a VoLTE outage. In this example, the mobile devices will implement an event-triggered “retry” procedure where the mobile device, upon detecting that the call cannot be established over VoLTE, tries to establish the call on a different, legacy RAT. In this scenario, the mobile device is unaware that there are no fallback RATs available to it, so the mobile device traverses through all of the possible layers, retrying on each, before it ultimately determines that the call cannot be established. A user of such a device may be frustrated by the failed call attempt, and may be further confused by the fact that the mobile device had indicated, before the call attempt, that voice service was available when in fact it was not (i.e., a false voice coverage indication). In emergency situations, a user of the mobile device may be unable to make a phone call to an emergency services telephone number (e.g., 911) in an LTE-only area when VoLTE is turned off.

DETAILED DESCRIPTION

Described herein are techniques and systems for implementing an idle mode process on a mobile device in order to selectively scan for legacy radio coverage using a timer-based scanning process. An LTE-compliant mobile device is configured to camp on a proximate cell site that employs LTE radio access using LTE communications protocol. When camped on the LTE-enabled cell site, the mobile device may transmit and/or receive communications to and/or from the cell site. When the mobile device is in an LTE-only area where the only available RAT available to the mobile device is the 4G LTE RAT, the mobile device can use VoLTE to transmit/receive voice communications, but is otherwise unable to use a legacy RAT for voice communications.

According to various embodiments, the mobile device may implement an idle mode process in order to determine whether it needs to be aware of its surroundings (i.e., the availability of legacy radio coverage) or not. In some embodiments, this determination involves evaluating one or more criteria that indicate whether the mobile device is capable of providing sufficient voice service capabilities over VoLTE. If the mobile device determines that being aware of its surroundings provides a positive net-benefit to the mobile device, a timer-based scanning procedure may be implemented to periodically (at regular or irregular time intervals) scan for the availability of legacy radio access technologies (RATs), even in the absence of an event, like a phone call attempt.

In some embodiments, a process to be implemented on a mobile device includes operating a mobile device in idle mode, establishing a LTE radio link between the mobile device and a cell site within communication range of the mobile device, and evaluating one or more of a plurality of criteria to decide whether to initiate a timer-based scanning process to scan for the availability of legacy radio coverage. In response to determining that none of the criteria are met (i.e., determining not to initiate the timer-based scanning process), the mobile device may stay camped on LTE (maintain the LTE radio link), and may provide an indicator indicating that the mobile device has voice service capabilities, all without (refraining from) scanning for availability of legacy coverage from a legacy RAN. In response to determining that at least one criterion is met, the mobile device may initiate the timer-based scanning process by monitoring a timer to determine whether a time period has expired, and upon determining that the time period has expired, the mobile device may scan for availability of legacy coverage from a legacy RAN. If, after scanning for legacy radio coverage, it is determined that legacy radio coverage is not available to the mobile device, the mobile device may provide an indicator indicating that the mobile device does not have voice service capabilities. If, on the other hand, it is determined that legacy radio coverage is available to the mobile device, the mobile device may provide an indicator indicating that the mobile device has voice service capabilities.

Also disclosed herein are systems comprising one or more processors and one or more memories, as well as non-transitory computer-readable media storing computer-executable instructions that, when executed, by one or more processors perform various acts and/or processes disclosed herein.

By implementing a timer-based scanning process selectively in instances where it benefits the mobile device to do so, the processor load on the mobile device is reduced and battery life extended by refraining from performing the timer-based scanning process when it provides little benefit to do so. Furthermore, when the timer-based scanning process is implemented, the timer-based process may execute at a frequency that allows the mobile device to maintain awareness of its surroundings without draining more battery than is necessary and without overloading the processor of the mobile device. Furthermore, a mobile device implementing the idle mode procedure described herein may be able to make wise, proactive decisions regarding what to surface to the user. That is, user experience is improved by accurately indicating whether the mobile device has voice service capabilities before a call is even attempted.

Example Environment

Although the techniques and systems disclosed herein are predominantly described with respect to 4G LTE networks and legacy RATs in terms of 3G and/or 2G RATs, it is to be appreciated that the techniques and systems described herein may be implemented in any future heterogeneous cellular network (e.g., a fifth generation (5G) network where 4G LTE might be considered a legacy RAT with respect to 5G, and so on). Thus, LTE, as it is used herein, may refer to current releases of LTE protocol, or any future evolution of LTE.

FIG. 1illustrates an example cellular network environment100that supports wireless communications between mobile devices, such as the mobile device102, and a cell site104. The cell site104ofFIG. 1may be configured to employ LTE radio access, and may also employ at least one legacy RAT, such as a 3G RAT and/or a 2G RAT. Accordingly, the cell site104may be capable of communicating wirelessly using any suitable wireless communications/data technology, protocol, or standard, such as Global System for Mobile Communications (GSM), Time Division Multiple Access (TDMA), Universal Mobile Telecommunications System (UMTS), Evolution-Data Optimized (EVDO), Long Term Evolution (LTE), Advanced LTE (LTE+), Generic Access Network (GAN), Unlicensed Mobile Access (UMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDM), General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Advanced Mobile Phone System (AMPS), High Speed Packet Access (HSPA), evolved HSPA (HSPA+), Voice over IP (VoIP), Voice over LTE (VoLTE), and/or any future IP-based network technology or evolution of an existing IP-based network technology.

FIG. 1further illustrates a user106who is associated with the mobile device102. The user106may have subscribed to services that a carrier (or cellular network operator) provides to its customers. In this manner, the user106(or subscriber) may access services from a core network using the mobile device102that communicates with the core network through the cell site104.

InFIG. 1, the user106is carrying the mobile device102within an “LTE-only area”108. The LTE-only area108is an area where the mobile device102is not within radio coverage of a legacy RAT, such as 3G/2G RATs. Instead, the only RAT available to the mobile device102is the 4G LTE RAT employed by the cell site104. In the example ofFIG. 1, the LTE-only area108is created because the radio coverage area of the LTE RAT is larger than the radio coverage area of any legacy RAT(s) employed by the cell site104. Accordingly, an overlap area110is also created around the cell site104where the legacy radio coverage overlaps with the LTE radio coverage. The result is the overlap area110where a heterogeneous cellular network is available to the mobile device102, and a “ring-shaped” the LTE-only area108having homogeneous radio coverage in the form of LTE.

Of course, the user106can carry the mobile device102with him/her to different locations, so the mobile device102may, at some different time, be located within the overlap area110, or outside (beyond) both the overlap area110and the LTE-only area108.FIG. 1illustrates the scenario when the mobile device102is within the LTE-only area108for illustrative purposes.

The mobile device102may be implemented as any suitable mobile computing device configured to communicate over a wireless network, including, without limitation, a mobile phone (e.g., a smart phone), a tablet computer, a laptop computer, a portable digital assistant (PDA), a wearable computer (e.g., electronic/smart glasses, a smart watch, fitness trackers, etc.), and/or any similar mobile device. In accordance with various embodiments described herein, the terms “wireless communication device,” “wireless device,” “communication device,” “mobile device,” and “user equipment (UE)” may be used interchangeably herein to describe any mobile device capable of performing the techniques described herein. The mobile device102may be capable of communicating wirelessly using any suitable wireless communications/data technology, protocol, or standard, such as GSM, TDMA, UMTS, EVDO, LTE, LTE+, GAN, UMA, CDMA, OFDM, GPRS, EDGE, AMPS, HSPA, HSPA+, VoIP, VoLTE, Institute of Electrical and Electronics Engineers (IEEE) 802.1x protocols, WiMAX, wireless fidelity (Wi-Fi™), and/or any future IP-based network technology or evolution of an existing IP-based network technology.

The mobile device102may operate in multiple operating modes. One example mode of operation may be an “active communications mode” where the mobile device102is actively communicating with (i.e., transmitting/receiving data to/from) the cell site104. The mobile device102may operate in the active communications mode during a call session, for example. Another example operating mode may be an “idle mode” where the mobile device102is not actively communicating with the cell site104. The mobile device102may operate in the idle mode when the user106is carrying the mobile device102in his/her pocket or a bag and the user106is not otherwise using the mobile device102for voice or data communications, streaming, or the like. It is to be appreciated that the mobile device102may operate in other operating modes, and is not limited to operating in just the two aforementioned operating modes.

In either operating mode (i.e., idle mode or active communications mode), the mobile device102may be camped on (or attached to) the cell site104. When the mobile device102and the cell site104have established a radio link, the mobile device102is said to be “camped on” the cell that is associated with the cell site104. The mobile device102within the LTE-only area108may attach to the cell site104by performing a registration for a packet-switched LTE network, and may thereby establish a LTE radio link with the cell site104. In instances where a legacy RAT is available to the mobile device102(e.g., if the mobile device102were to move within the overlap area110), the mobile device102may attach to the cell site104using a “combined attach” procedure where the mobile device102performs registration for both a circuit-switch (non-LTE) network and a packet-switched (LTE) network. By being “combined attached” to the cell site104, the mobile device102may implement CSFB so that a legacy RAT can be used for a voice call in the event that VoLTE functionality fails or is rendered unusable.

FIG. 1further illustrates that the mobile device102may be configured to implement an idle mode process112. The idle mode process112may execute as a background process by executing processor-executable instructions stored on the mobile device102, and may be executed at start-up, and/or at multiple different times (e.g., periodically), and the like. A more detailed process will be discussed below with reference toFIG. 4according to various embodiments.

At114, the mobile device102may be operating in idle mode and may be camped on a LTE network cell employed by the cell site104. The mobile device102operating in idle mode at114may perform a registration for the packet-switched LTE network in order to attach to (camp on) the LTE network cell provided by the cell site104.

At116, a client application on the mobile device102may determine whether to initiate a timer-based scanning process that scans for legacy radio coverage. At a high level, if the mobile device102determines, at116, that it can provide sufficient voice communications services over LTE (i.e., following the “no” route from116), the mobile device102, at step118, stays camped on LTE and refrains from scanning for legacy radio coverage. In other words, if the mobile device102is not reliant on a legacy network for any reason, there is no need to scan for legacy radio coverage. The idle mode process112may iterate from118by returning to114and proceeding to decision block116.

In some embodiments, the determination at116may involve evaluation of one or more of a plurality of criteria including: (i) whether the mobile device102is not capable of utilizing VoLTE communications through or with the cell site104via a LTE RAT employed by the cell site104; (ii) whether a VoLTE capability of the mobile device102has been turned off; and/or (iii) whether the mobile device102is not capable of making a call to an emergency services telephone number (e.g., E911) using VoLTE. If any of the aforementioned criteria are met, the idle mode process112may follow the “yes” route from116, which indicates that the mobile device102is at risk of not having voice service capabilities. That is, unless the mobile device102can identify an available legacy RAT (e.g., 3G/2G) to “fall back on,” it may not be able to provide voice services for the user106.

Following the “yes” route from decision block116, the idle mode process112may proceed to step120where a timer-based scanning process may be initiated to scan for legacy radio coverage. The scanning process at120is timer-based in the sense that scanning is executed based on a timer (i.e., expiration of a time interval). In the example ofFIG. 1, the mobile device102is shown as being located within the LTE-only area108, and, therefore, the timer-based scanning process, upon execution at120, may indicate to the mobile device102that there is no available legacy radio coverage. As a result, the mobile device102may indicate (e.g., on a display of the mobile device102, a light emitting diode (LED) indicator, etc.) that the mobile device102is out of voice coverage (i.e., it does not have voice service capabilities). In the absence of the scanning process at120, a different mobile device may provide a false coverage indication that the mobile device has LTE coverage when in fact it doesn't. The idle mode process112may iterate from120by returning to114and proceeding to decision block116.

By implementing the idle mode process112, the mobile device102may selectively scan for legacy radio coverage using a timer-based scanning process at120in instances where it benefits the mobile device102to initiate the scanning process at120. In other words, if the mobile device102determines that there is a negative net-benefit to performing the scanning at120(i.e., the mobile device102can provide sufficient voice communications using VoLTE), the idle mode process112loops through the “no” route at116without going to step120.

FIG. 2illustrates an example cellular network environment200that supports wireless communications between mobile devices and multiple different cell sites, including cell site202and cell site204.FIG. 2illustrates a different environment200and a different scenario thanFIG. 1. First, the cell site202may be configured to employ LTE radio access, but may not be configured to employ a legacy RAT, such as 3G or 2G RATs. Thus, the cell site202ofFIG. 2illustrates the “green field” scenario where a carrier may have acquired new cell site for LTE, and no legacy layers have been placed underneath the LTE layer. The “green field” scenario is yet another cause for the creation of LTE-only areas, such as the LTE-only area108.

FIG. 2further illustrates cell site204that may employ at least one legacy RAT, such as a 3G RAT and/or a 2G RAT. In the example ofFIG. 2, the radio coverage of the legacy RAT(s) provided by the cell site204partially overlaps with the radio coverage area of the cell site202, thereby creating the overlap area110. The LTE-only area108and the overlap area110, although created differently, may have similar properties and characteristics to those described with reference toFIG. 1.FIG. 2also shows a legacy area206where LTE radio access may or may not exist. For example, a legacy-only cell site204may not employ 4G LTE radio access, and in this case, the legacy area206may be a legacy-only area. It is to be appreciated that the legacy area may alternatively be a heterogeneous RAT area where both legacy and LTE radio access is available.

The user106inFIG. 2is shown to be carrying his/her mobile device102within the overlap area110, meaning that the mobile device102is within coverage of both LTE and legacy RATs. The mobile device102may implement the idle mode process112. In the scenario ofFIG. 2, the mobile device102may be combined attached to both the LTE network cell provided by the cell site202and the circuit-switched legacy network cell provided by the cell site204.

In a similar fashion to the scenario ofFIG. 1, during execution of the idle mode process112, if the mobile device determines, at116, that it can provide sufficient voice communications services over LTE (i.e., following the “no” route from116), the mobile device102, at step118, stays camped on LTE via the cell site202and refrains from scanning for legacy radio coverage. In other words, if the mobile device102is not reliant on a legacy network provided by the cell site204, there is no need to scan for legacy radio coverage.

However, following the “yes” route from decision block116(i.e., the mobile device102determines that it may need a legacy RAT to provide sufficient voice communications), the idle mode process112may initiate the timer-based scanning process at120to scan for legacy radio coverage. In the example ofFIG. 2, the mobile device102is shown as being located within the overlap area110, and, therefore, the timer-based scanning process, upon execution at120, may indicate to the mobile device102that legacy radio coverage is available (in this case, from the cell site204). As a result, the mobile device102may indicate (e.g., on a display of the mobile device102, a LED indicator, etc.) that the mobile device102is within voice coverage (i.e., it has voice service capabilities). The indicator provided by the mobile device102may vary depending on the type of legacy coverage available to the mobile device102. For example, if a first carrier (or cellular network operator) provides the LTE coverage using the cell site202, and a second, different carrier provides legacy 3G/2G coverage using the cell site204, and if there is no roaming agreement between the first and second carriers, the mobile device102may indicate that it has “limited service” and may camp on the cell provided by cell site204in a limited service mode, meaning that the mobile device102does not have sufficient credentials and/or is not authorized to receive the legacy RAT service for normal calls, but can still make emergency calls (e.g., E911) over the second carrier's legacy RAT system.

It is to be appreciated that although the shapes of the radio coverage areas shown inFIGS. 1 and 2are circular, the radio coverage footprint from any one or more of the cell sites inFIGS. 1 and 2may be of any suitable shape, such as square, triangular, hexagonal, or any suitable polygonal shape.

FIG. 3is a block diagram of an example architecture of the mobile device102in accordance with various embodiments. As shown, the mobile device102may include one or more processors300and one or more forms of computer-readable memory302. The mobile device102may also include additional storage devices. Such additional storage may include removable storage304and/or non-removable storage306.

In various embodiments, the computer-readable memory302generally includes both volatile memory and non-volatile memory (e.g., random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EEPROM), Flash Memory, miniature hard drive, memory card, optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium). The computer-readable memory302may also be described as computer storage media and may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Computer-readable memory302, as well as the removable storage304and non-removable storage306, are all examples of computer-readable storage media. Computer-readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by the mobile device102. Any such computer-readable storage media may be part of the mobile device102.

The mobile device102may further include input devices308, including, without limitation, a touch screen (e.g., touch, or proximity-based) display, physical buttons (e.g., keyboard or keypad), a camera-based sensor configured to receive gestural input from a user, a microphone or microphone array for receiving voice input commands from a user, pointing devices (e.g., mouse, pen, stylus, etc.), or any other suitable input devices308coupled communicatively to the processor(s)300and the computer-readable memory302. The mobile device102may further include output devices310, including, without limitation, a display, one or more LED indicators, speakers, a printer, or any other suitable output device coupled communicatively to the processor(s)300and the computer-readable memory302.

The mobile device102may further include communications connection(s)312that allow the mobile device102to communicate with other computing devices314such as via a network (e.g., an IP Multimedia Subsystem (IMS) network). The communications connection(s)312may facilitate transmitting and receiving wireless signals over any suitable wireless communications/data technology, standard, or protocol, as described above, such as using licensed, semi-licensed, or unlicensed spectrum over a telecommunications network. For example, the communication connection(s)312may represent one or more of a cellular radio, a wireless (e.g., IEEE 802.1x-based) interface, a Bluetooth® interface, and so on. In some embodiments, the communications connection(s)312may include radio frequency (RF) circuitry that allows the mobile device102to transition between different RATs, such as transitioning between communication with a 4G LTE RAT and a legacy RAT (e.g., 3G/2G). The communications connection(s)312may further enable the mobile device102to communicate over circuit-switch domains and/or packet-switch domains.

In some embodiments, the computer-readable memory302may include VoLTE evaluator316and a RAT scanner318, among other possible modules, data structures, and/or processor-readable instructions. The VoLTE evaluator316may be configured to evaluate one or more of a plurality of criteria as part of the idle mode process112. For example, the VoLTE evaluator316may evaluate whether the mobile device102is not capable of utilizing VoLTE communications through or with a proximately located (within range) cell site via a LTE RAT employed by the cell site. This criterion may be satisfied when the mobile device102is not a VoLTE capable device, which may be the case for some older models of mobile devices102that are still usable over LTE networks, but operate on a circuit-switch domain for voice calling.

As another example, the VoLTE evaluator316may evaluate whether a VoLTE capability of the mobile device102has been turned off. For example, the mobile device102may allow the user106to manually turn off a VoLTE capability of the mobile device102. In some embodiments, this may be enabled through user input received via the input device(s)308(e.g., a touch screen user input, voice command, etc.) to disable the VoLTE capability on the mobile device102. In other embodiments, the user106may access a settings menu to set conditions when the VoLTE capability is to be automatically turned off by the mobile device102(e.g., based on location, the availability of a Wi-Fi AP, etc.).

As yet another example, the VoLTE evaluator316may evaluate whether the mobile device102is not capable of making a call to an emergency services telephone number (e.g., E911) using VoLTE. The reason for evaluating this criterion is due to the fact that, even when the VoLTE capability of the mobile device102is turned on, the mobile device102may not support E911 because E911 voice communications may be handed over to legacy RATs as opposed to transmitting over VoLTE. This can be an issue for carriers because carriers are to support both regular calls and E911 calls.

If the VoLTE evaluator316determines that any of the aforementioned criteria are satisfied/met, it may indicate that the mobile device102is at risk of not having voice service capabilities. That is, unless the mobile device102can identify an available legacy RAT (e.g., 3G/2G) to “fall back on,” it may not be able to provide sufficient voice services for the user106.

The RAT scanner318may be configured to cause the mobile device102, via the communication connection(s)312to scan for legacy radio coverage. The RAT scanner318is selectively utilized based on the determination from the VoLTE evaluator316as to whether the RAT scanner318needs to initiate scanning. If the VoLTE evaluator316indicates to the RAT scanner318that the availability of legacy radio coverage is to be determined, the RAT scanner318may utilize a timer to determine when to scan for legacy radio coverage. In some embodiments, the timer may be implemented on the mobile device102in the form of a software-based timer320or a hardware-based timer322(e.g., a timer implemented via a microcontroller), In other embodiments, the timer may be implemented on a network, such as an IMS network, where the mobile device102may monitor a remote timer324via the communications connection(s)312, such as by polling a remote computing resource (e.g., the other computing devices314), or otherwise receiving a signal or communication as to whether a time period has expired. In the network-provided timer implementation, the network-accessible remote timer324may be configured to control a plurality of mobile devices, including the mobile device102, to enforce a universal or global time period so that the plurality of mobile devices behave similarly in terms of the frequency in which the RAT scanner318scans for legacy coverage. The timer320,322, or324controls the frequency at which the scanning occurs. For example, if the timer-based scanning process is initiated, the RAT scanner318may cause scanning for legacy radio coverage every 10 seconds. Any suitable time interval may be chosen and is configurable per the implementation on the mobile device102.

Example Processes

FIG. 4illustrates a flowchart of an example idle-mode process400for selectively scanning for legacy radio coverage. The process400may represent a more detailed process of the idle mode process112described with reference to the previous figures. The process400may be implemented by the mobile device102and relevant components of the mobile device102, such as the VoLTE evaluator316, the RAT scanner318, the software-based timer320, the hardware-based timer322, or the remote timer324, and the communication connection(s)312, among other components.

At402, the mobile device102may be operating in idle mode and may be camped on a LTE network cell, such as the cell site104ofFIG. 1or the cell site202ofFIG. 2. The mobile device102operating in idle mode at402may perform a registration for the packet-switched LTE network in order to attach to (camp on) the LTE network cell. In some embodiments a combined attach process may be used to attach the mobile device102to both a circuit-switched non-LTE network and a packet-switched LTE network. In some embodiments, upon establishing a radio link with an LTE network cell, the mobile device102may provide a default indicator (e.g., a visual indicator provided on the display, an LED indicator, etc.) indicating that the mobile device102is within coverage for voice and data communications.

At decision blocks404,406, and408, the VoLTE evaluator316may evaluate various criteria in order to determine whether to initiate a timer-based scanning process that scans for legacy radio coverage. At a high level, if the VoLTE evaluator316determines, at404-408, that it can provide sufficient voice communications services over LTE, the idle mode process400stays within Branch1by refraining from scanning for legacy radio coverage and staying camped on the LTE network cell. Otherwise, the idle mode process400moves to Branch2to initiate the timer-based scanning process if the VoLTE evaluator316determines that the mobile device102may be reliant on a legacy network for voice communications.

At404, the VoLTE evaluator316may evaluate whether the mobile device102is capable of utilizing VoLTE communications through or with a cell site that employs the LTE RAT the mobile device102is camped on. If not, (e.g., the mobile device102is an older device that does not support VoLTE communications for voice), the process400may proceed to Branch2. If the mobile device102is capable of utilizing VoLTE, the process400may proceed to406.

At406, the VoLTE evaluator316may evaluate whether a VoLTE capability of the mobile device102has been turned off (e.g., by the user106via user input, by the device102due to a control setting, etc.). If the VoLTE capability is off, the process400may proceed to Branch2. If the VoLTE capability is on, the process400may proceed to408.

At408, the VoLTE evaluator316may evaluate whether the mobile device102is capable of making a call to an emergency services telephone number (e.g., E911) using VoLTE. If not, the process400may proceed to Branch2. If the mobile device102is capable of utilizing VoLTE for emergency calls, the process400may proceed to410.

At410, having determined that there is a negative net-benefit to scanning for legacy radio coverage, the mobile device102may continue to provide an indicator (e.g., a display indicator) indicating that the mobile device102that the mobile device102has sufficient voice service capabilities and can, when needed, establish voice communications over VoLTE. The mobile device410also refrains from scanning for legacy radio coverage by avoiding Branch2.

At412, a determination may be made as to whether the VoLTE capability has been turned off on the mobile device102. For example, the user106may manually (e.g., via touch screen user input) turn off the VoLTE capability on the mobile device102. If the toggling of the VoLTE capability to “off” is detected at412, the process400iterates by returning to402.

At414, so long as the VoLTE capability remains turned “on” and is enabled, a timer may be monitored to determine whether a time period has expired. If not, the process400may loop back to410in order to proceed through decision blocks412and414again. Once the timer expires at414, the process400may iterate by returning to402so that the criteria can be evaluated again at404-408. In this manner, the idle mode process400may stay within Branch1so long as sufficient VoLTE capabilities are available for voice communications.

Returning again to the “no” routes from decision blocks404-408, if the VoLTE evaluator316determines that the “no” route for any one of the criteria at404-408is to be followed, the idle mode process400initiates a timer-based scanning process represented by Branch2shown inFIG. 4. Branch2is initiated when it is determined that the mobile device102is at risk of not having voice service capabilities. That is, unless the mobile device102can identify an available legacy RAT (e.g., 3G/2G) to “fall back on,” it may not be able to provide voice services for the user106.

At416, a timer, such as the software-based timer320, the hardware-based timer322, or the remote timer324, may be monitored, and at418, a determination is made as to whether the timer320,322, or324has expired. If the timer has not expired, the process400iterates back to416and loops until it is determined at418that the timer has expired. In this manner, battery of the mobile device102may be conserved by selecting a scanning frequency, as implemented by the time period monitored at416, that high enough to maintain awareness of legacy radio coverage, but not so high that battery is unnecessarily drained. In some embodiments, when Branch2is entered for the first time after startup of the mobile device102, the process may proceed from404,406, or408directly to420so as to avoid a situation where the user106initiates a call before the timer has expired. On subsequent iterations, however, the timer may be monitored at416.

At420, upon expiration of the timer (or time period), the RAT scanner318may cause the mobile device102to utilize its cellular radio (i.e., the communication connection(s)312) to scan for the availability of legacy (e.g., 3G/2G) radio coverage. Because there may be different types of legacy radio coverage available to the mobile device102, decision blocks422and424evaluated.

At422, a determination is made, based on the scan at420, whether there is legacy coverage from a home carrier (i.e., a carrier used by the mobile device102), or a partner of the home carrier who is in a roaming agreement with the home carrier. In other words, the determination at422is a determination of whether there is an available legacy RAN that the mobile device102is authorized (e.g., has the proper credentials) to use. If there is such a home or partner legacy RAN available at422, the process400iterates back to402, and the mobile device may continue to indicate (e.g., via the display) that it has sufficient voice coverage, and may stay camped on the LTE network cell. In this scenario, if the user106were to make a call using the mobile device, the mobile device102may invoke CSFB to establish the voice communications over the legacy RAN that the mobile device102is authorized to use.

If the RAT scanner318does not find an available home or partner legacy RAN at422, the a determination may be made at424as to whether there is an available non-roaming partner legacy RAN. For example, a particular carrier may provide a legacy RAT through a cell site that is available to the mobile device, but the particular carrier may not have a roaming agreement with the home carrier that provides IMS services to the mobile device102. In other words, the determination at422is a determination as to whether there is an available legacy RAN that the mobile device102is not authorized to use. If there is such a non-roaming partner legacy RAN, the mobile device102may provide, at426, a “limited service” indicator, and the mobile device102may camp on the LTE network cell in a “limited service” mode, meaning that the mobile device102cannot make normal calls, but can still make emergency calls (e.g., E911) over the RAT system identified at424. If, on the other hand, no legacy radio coverage is detected at both422and424, the mobile device102may provide, at428, a “no service” indicator to indicate that the mobile device102does not have voice service capabilities. The mobile device102may also disable an LTE radio link at426. The process400may iterate from426and428, depending on which route is followed from decision block424.

An example downstream use of the timer-based scanning process of Branch2shown inFIG. 4is for reducing the time and processing required for load-based handovers. For example, if, while operating in the active communications mode over an LTE RAN, the mobile device102determines to perform a load-based handover to a legacy RAN because the LTE network is above some threshold load, the mobile device102may be configured to eliminate a scanning step involved with load-based handovers if the mobile device102has recently traversed Branch2of the idle mode process400. This may save time and processing involved with load-based handovers.

The environment and individual elements described herein may of course include many other logical, programmatic, and physical components, of which those shown in the accompanying figures are merely examples that are related to the discussion herein.

The various techniques described herein are assumed in the given examples to be implemented in the general context of computer-executable instructions or software, such as program modules, that are stored in computer-readable storage and executed by the processor(s) of one or more computers or other devices such as those illustrated in the figures. Generally, program modules include routines, programs, objects, components, data structures, etc., and define operating logic for performing particular tasks or implement particular abstract data types.