Enhanced system acquisition while roaming

Various methods, apparatus, and computer readable media are disclosed for enhanced system acquisition while a user equipment (UE) is roaming. The UE may detect roaming from a coverage area associated with a first public land mobile network (PLMN) supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data. In response to the detection, the UE may store data corresponding to the second PLMN such that the second PLMN is a registered PLMN (RPLMN). The UE may initiate system acquisition, wherein the system acquisition includes searching for the RPLMN prior to searching for any other PLMN. The other PLMN may include a home PLMN (HPLMN). The coverage area associated with the first PLMN may be within a first country, and the coverage area associated with the second network may be within a second country different from the first country.

TECHNICAL FIELD

The technology discussed below relates generally to wireless communication and, more particularly, to system acquisition while roaming in a wireless communication network.

INTRODUCTION

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Many wireless communication technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of a telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. For example, the quality of service of voice communications utilizing the packet switched LTE network remains less than that available in existing, circuit switched networks. For example, 3GPP networks such as UMTS and GSM, and networks defined by other standards bodies, such as the cdma2000 1× networks promulgated by 3GPP2, continue to be relied upon for their circuit switched voice communication capabilities.

BRIEF SUMMARY OF SOME EXAMPLES

In an aspect, the disclosure provides a method of wireless communication that includes detecting roaming from a coverage area associated with a first public land mobile network (PLMN) supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data. The method also includes, in response to the detecting, storing data corresponding to the second PLMN such that the second PLMN is a registered PLMN (RPLMN). The method also includes initiating system acquisition, wherein the system acquisition includes searching for the RPLMN prior to searching for any other PLMN.

In another aspect, the disclosure provides an apparatus for wireless communication, and the apparatus includes a memory, a transceiver, and at least one processor communicatively coupled to the memory and the at least one processor. The at least one processor is configured for detecting roaming from a coverage area associated with a first PLMN supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data. The at least one processor is also configured for storing, in response to the detecting, data corresponding to the second PLMN in the memory such that the second PLMN is an RPLMN. The at least one processor is also configured for initiating system acquisition, wherein the system acquisition includes searching for the RPLMN prior to searching for any other PLMN.

In yet another aspect, the disclosure provides another apparatus for wireless communication. The apparatus includes means for detecting roaming from a coverage area associated with a first PLMN supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data. The apparatus also includes means for storing, in response to the detecting, data corresponding to the second PLMN such that the second PLMN is an RPLMN. The apparatus also includes means for initiating system acquisition, wherein the system acquisition includes searching for the RPLMN prior to searching for any other PLMN.

In a further aspect, the disclosure provides a computer-readable medium that includes computer-executable instructions. The computer-executable instruction are configured for detecting roaming from a coverage area associated with a first PLMN supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data. The computer-executable instructions are also configured for storing, in response to the detecting, data corresponding to the second PLMN such that the second PLMN is an RPLMN. The computer-executable instructions are also configured for initiating system acquisition, wherein the system acquisition comprises searching for the RPLMN prior to searching for any other PLMN.

DETAILED DESCRIPTION

FIG. 1is a diagram100illustrating an example of a hardware implementation of a user equipment (UE)102. In some configurations, the UE102may include a user interface112. The user interface112may be configured to receive one or more inputs from a user of the UE102. The user interface112may also be configured to display information to the user of the UE102. The user interface112may exchange data to and/or from the UE102via the bus interface108. The UE102may also include a transceiver110. The transceiver110may be configured to receive data and/or transmit data in communication with another apparatus. The transceiver110provides a means for communicating with another apparatus via a wired and/or wireless transmission medium. The transceiver110may be configured to perform such communications using various types of technologies. One of ordinary skill in the art will understand that many types of technologies to perform such communication may be used without deviating from the scope of the present disclosure. The UE102may also include a memory114, one or more processors104, a computer-readable medium106, and a bus interface108. The bus interface108may provide an interface between a bus103and the transceiver110. The memory114, the one or more processors104, the computer-readable medium106, and the bus interface108may be connected together via the bus103. The processor104may be communicatively coupled to the transceiver110and/or the memory114.

The processor104may include a roam detection circuit120, a storage circuit121, a system acquisition circuit122, a control circuit123, and/or other circuits (not shown). Generally, the roam detection circuit120, the storage circuit121, the system acquisition circuit122, the control circuit123, and/or the other circuits (not shown) may, individually or collectively, include various hardware components and/or software modules that can perform and/or enable any one or more of the functions, methods, operations, processes, features and/or aspects described herein with reference to an apparatus. The roam detection circuit120provides the means for detecting roaming from the coverage area associated with the first PLMN supporting hybrid voice and data to the coverage area associated with the second PLMN without support for hybrid voice and data. The storage circuit121provides the means for storing, in response to the detection, data corresponding to the second PLMN such that the second PLMN is the RPLMN. The system acquisition circuit122provides the means for initiating system acquisition, wherein system acquisition may include searching for the RPLMN prior to searching for any other PLMN.

In some configurations, the control circuit123provides the means for comparing information associated with the second PLMN with stored information associated with PLMNs that support hybrid voice and data. In such configurations, the control circuit123also provides the means for determining that the second PLMN is without support for hybrid voice and data when the information associated with the second PLMN does not match the stored information associated with the PLMNs that support hybrid voice and data. In some configurations, the control circuit123also provides the means for switching communication from hybrid voice and data to circuit-switched fallback (CSFB) after determining that the second PLMN is without support for hybrid voice and data.

The foregoing description provides a non-limiting example of the processor104of the UE102. Although various circuits have been described above, one of ordinary skill in the art will understand that the processor104may also include various other circuits (not shown) that are in addition and/or alternative(s) to the aforementioned circuits120,121,122,123. Such other circuits (not shown) may provide the means for performing any one or more of the functions, methods, operations, processes, features and/or aspects described herein with reference to the apparatus.

The computer-readable medium106includes various computer executable instructions. The computer-executable instructions may be executed by various hardware components (e.g., processor104, or any one or more of its circuits120,121,122,123) of the UE102. The instructions may be a part of various software programs and/or software modules. The computer-readable medium106may include roam detection instructions140, storage instructions141, system acquisition instructions142, control instructions143, and/or other instructions (not shown). Generally, the roam detection instructions140, the storage instructions141, the system acquisition instructions142, the control instructions143, and/or the other instructions (not shown) may, individually or collectively, be configured for performing and/or enabling any one or more of the functions, methods, operations, processes, features and/or aspects described herein with reference to an apparatus.

The roam detection instructions140include computer-executable instructions configured for detecting roaming from the coverage area associated with the first PLMN supporting hybrid voice and data to the coverage area associated with the second PLMN without support for hybrid voice and data. The storage instructions141include computer-executable instructions configured for storing, in response to the detection, data corresponding to the second PLMN such that the second PLMN is the RPLMN. The system acquisition instructions142include computer-executable instructions configured for initiating system acquisition, wherein system acquisition may include searching for the RPLMN prior to searching for any other PLMN.

In some configurations, the control instructions143include computer-executable instructions configured for comparing information associated with the second PLMN with stored information associated with PLMNs that support hybrid voice and data. In such configurations, the control instructions143also include computer-executable instructions configured for determining that the second PLMN is without support for hybrid voice and data when the information associated with the second PLMN does not match the stored information associated with the PLMNs that support hybrid voice and data. In some configurations, the control instructions143also include computer-executable instructions configured for switching communication from hybrid voice and data to CSFB after determining that the second PLMN is without support for hybrid voice and data.

The foregoing description provides a non-limiting example of the computer-readable medium106of the UE102. Although various computer-executable instructions (e.g., computer-executable code) have been described above, one of ordinary skill in the art will understand that the computer-readable medium106may also include various other instructions (not shown) that are in addition and/or alternative(s) to the aforementioned computer-executable instructions140,141,142,143. Such other instructions (not shown) may include computer-executable instructions configured for performing any one or more of the functions, methods, processes, operations, features and/or aspects described herein with reference to an apparatus.

The memory114may include various memory modules. The memory modules may be configured to store, and have read therefrom, various values and/or information by the processor104, or any of the aforementioned circuits120,121,122,123. The memory modules may also be configured to store, and have read therefrom, various values and/or information upon execution of the computer-executable code included in the computer-readable medium106, or any of the aforementioned computer-executable instructions140,141,142,143.

As described above, the storage circuit121and/or the storage instructions141provide for storing certain data corresponding to the second PLMN. Such data may include system information associated with the second PLMN and is described in greater detail below. In some configurations, such data is stored in the Subscriber Identity Module (SIM) module130of the memory114. However, one of ordinary skill in the art will understand that such information may additionally or alternatively be stored in various other components without deviating from the scope of the present disclosure.

As also described above, the control circuit123and/or the control instructions143provide for comparing information associated with the second PLMN with stored information associated with PLMNs that support hybrid voice and data. In some configurations, the information associated with the second PLMN is the Mobile Country Code (MCC) associated with the second PLMN, and the information associated with the PLMNs that support hybrid voice and data is a list of MCCs. Such information may be stored in the MCC module132of the memory114. However, one of ordinary skill in the art will understand that such information may additionally or alternatively be stored in various other components without deviating from the scope of the present disclosure.

One of ordinary skill in the art will also understand that the UE102may include alternative and/or additional elements without deviating from the scope of the present disclosure. In accordance with some aspects of the present disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a UE102that includes one or more processors104. Examples of the one or more processors104include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. The UE102may be implemented with a bus architecture, represented generally by the bus103and bus interface108. The bus103may include any number of interconnecting buses and bridges depending on the specific application of the UE102and the overall design constraints. The bus103may link together various circuits including the one or more processors104, the memory114, and the computer-readable media106. The bus103may also link various other circuits, such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art.

The one or more processors104may be responsible for managing the bus103and general processing, including the execution of software stored on the computer-readable medium106. The software, when executed by the one or more processors104, causes the UE102to perform the various functions described below for any one or more apparatuses. The computer-readable medium106may also be used for storing data that is manipulated by the one or more processors104when executing software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on the computer-readable medium106. The computer-readable medium106may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium106may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium106may reside in the UE102, external to the UE102, or distributed across multiple entities including the UE102. The computer-readable medium106may be embodied in a computer program product. By way of example and not limitation, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

FIG. 2is a diagram200illustrating a network architecture employing various apparatuses. A non-limiting example of such a network architecture is an LTE network architecture. The LTE network architecture may sometimes be referred to as an Evolved Packet System (EPS). The EPS may include one or more user UEs102, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)204, an Evolved Packet Core (EPC)210, a Home Subscriber Server (HSS)220, and an Operator's Internet Protocol (IP) Services222. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown.

The EPS provides packet-switched services; however, as those skilled in the art will readily appreciate, various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services. For example, as illustrated inFIG. 2, the UE102is being capable of utilizing a communication link to a circuit-switched (CS) network230. In some configurations, the UE102may communicate with the CS network230separately from its communication with the evolved node B (eNB)206. In some other configurations, the serving eNB206may be capable of communicating with the CS network230on behalf of the UE102. The CS network may utilize any suitable protocol or communication standard capable of circuit-switched communication, including but not limited to a UMTS network utilizing W-CDMA, TD-SCDMA or any other air interface; a 3GPP2 network such as cdma2000 1×; an IEEE 802.16 WiMAX network; or any other suitable network or combination of networks. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.

The E-UTRAN204includes the evolved Node B (eNB)206and other eNBs208. The eNB206provides user and control plane protocol terminations toward the UE102. The eNB206may be connected to the other eNBs208via an X2 interface (e.g., a backhaul). The eNB206may also be referred to by those skilled in the art as a base station (BS), a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The eNB206provides an access point to the EPC210for a UE102. Examples of UEs102include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The UE102may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

The eNB206is connected by an S1 interface to the EPC210. The EPC210includes a Mobility Management Entity (MME)212, other MMEs214, a Serving Gateway216, and a Packet Data Network (PDN) Gateway218. The MME212is the control node that processes the signaling between the UE102and the EPC210. Generally, the MME212provides bearer and connection management. All user IP packets are transferred through the Serving Gateway216, which itself is connected to the PDN Gateway218. The PDN Gateway218provides UE IP address allocation as well as other functions. The PDN Gateway218is connected to the Operator's IP Services222. The Operator's IP Services222includes the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a packet-switched (PS) Streaming Service (PSS).

For voice communication, the UE102may utilize any one or more of several schemes. For example, voice may be packetized and communicated via the EPS by way of the IMS. As another example, voice communication may utilize circuit-switched channels by way of the CS network230. Depending on which network operator the UE102is communicating with, different schemes for CS voice communication may be utilized. Various non-limiting examples various communication types, schemes, modes, operations, methods, and/or processes are described in greater detail below (e.g., with reference toFIG. 5) and therefore will not be repeated here.

The radio protocol architecture may take on various forms depending on the particular application. An example for an LTE system will now be presented with reference toFIG. 3.FIG. 3is a diagram300illustrating an example of the radio protocol architecture for the user and control planes. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 is the lowest layer and implements various physical layer signal processing functions. Layer 1 will be referred to herein as the physical layer306. Layer 2 (L2 layer)308is above the physical layer306and is responsible for the link between the UE and eNB over the physical layer306.

In the user plane, the L2 layer308includes a media access control (MAC) sublayer310, a radio link control (RLC) sublayer312, and a packet data convergence protocol (PDCP)314sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer308including a network layer (e.g., IP layer) that is terminated at the PDN gateway218(seeFIG. 2) on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.).

In the control plane, the radio protocol architecture for the UE102and eNB206is substantially the same for the physical layer306and the L2 layer308with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer316in Layer 3. The RRC sublayer316is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB206and the UE102.

FIG. 4is a diagram400of the UE102in communication with a network node (e.g., eNB206). In the downlink (DL), upper layer packets from the core network are provided to a controller/processor475. The controller/processor475implements the functionality of the L2 layer described earlier in connection withFIG. 3. In the DL, the controller/processor475provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE102based on various priority metrics. The controller/processor475is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE102.

The RX processor456implements various signal processing functions of the L1 layer. The RX processor456performs spatial processing on the information to recover any spatial streams destined for the UE102. If multiple spatial streams are destined for the UE102, they may be combined by the RX processor456into a single OFDM symbol stream. The RX processor456then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB206. These soft decisions may be based on channel estimates computed by the channel estimator458. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB206on the physical channel. The data and control signals are then provided to the controller/processor459.

The controller/processor459implements the L2 layer described earlier in connection withFIG. 3. In the UL, the control/processor459provides de-multiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink462, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink462for L3 processing. The controller/processor459is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.

In the uplink (UL), a data source467is used to provide upper layer packets to the controller/processor459. The data source467represents all protocol layers above the L2 layer (L2). Similar to the functionality described in connection with the DL transmission by the eNB206, the controller/processor459implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB206. The controller/processor459is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB206.

Channel estimates derived by a channel estimator458from a reference signal or feedback transmitted by the eNB206may be used by the TX processor468to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor468are provided to different antenna452via separate transmitters454TX. Each transmitter454TX modulates an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB206in a manner similar to that described in connection with the receiver function at the UE102. Each receiver418RX receives a signal through its respective antenna420. Each receiver418RX recovers information modulated onto an RF carrier and provides the information to a RX processor470. The RX processor470implements the L1 layer.

The controller/processor459implements the L2 layer described earlier in connection withFIG. 3. In the UL, the control/processor459provides de-multiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE102. Upper layer packets from the controller/processor475may be provided to the core network. The controller/processor459is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

FIG. 5is a diagram500illustrating an example of the UE102communicating with networks supporting CSFB and/or hybrid voice and data. A first network502supports hybrid voice and data. (This network502may also support CSFB but hybrid voice and data may be preferred over CSFB because hybrid voice and data may provide a better user experience relative to CSFB.) Generally, the term ‘hybrid voice and data’ may refer to any technology that enables simultaneous and/or concurrent communication of voice and data. A non-limiting example of hybrid voice and data includes simultaneous voice and LTE (SVLTE) technology. With regard to SVLTE, the UE102may utilize two radio circuits: one for LTE communication, and the other for communication with the CS network230. The UE102may be enabled to simultaneously utilize both of the radio circuits to enable the SVLTE technology. Another non-limiting example of hybrid voice and data includes single radio LTE (SRLTE). With regard to SRLTE, the UE102may be enabled to simultaneously communicate with the CS network230and the EPS utilizing a single radio circuit. SRLTE may refer to a variation of SVLTE technology. SVLTE and SRLTE, together, may sometimes be referred to as SXLTE. One of ordinary skill in the art will understand that SVLTE, SRLTE, SXLTE, and/or ‘hybrid voice and data’ may refer to any simultaneous voice and data technology, including both single-radio and dual-radio technologies, without deviating from the scope of the present disclosure.

If hybrid voice and data is not available to the UE102, the UE102may utilize what is sometimes referred to as circuit-switched fallback (CSFB). In CSFB, the EPS is utilized for data communication. When a circuit-switched voice call is desired, the UE102ceases the LTE communication and ‘falls back’ to a 3G or other suitable circuit-switched technology for the voice call. With CSFB, data on the LTE network and voice on the 3G network are not possible simultaneously.

A second network504supports CSFB without providing support for hybrid voice and data. As illustrated inFIG. 5, hybrid voice and data enables communication of voice or data. In CSFB, the UE102is not enabled to communicate voice and data concurrently nor simultaneously. In some configurations, the UE102may utilize a single communication link with a circuit-switched network for communication of either voice or data. Such a communication link may not exist concurrently with another communication link that provides data or voice, respectively. In some configurations, the UE102may utilize a single software stack for either voice service or data service. However, in CSFB, the UE102may not utilize that single software stack for concurrent nor simultaneous voice and data service.

To enable hybrid voice and data, the first network502supporting hybrid voice and data may utilize the MME212, which is described in greater detail above with reference toFIG. 2. To enable data services, the second network504may utilize a Serving General Packet Radio Service (GPRS) Support Node (SGSN)506. To enable voice services, the second network504may utilize a Mobile Switching Center (MSC) server508. The MSC server508may connect to the carrier's telephony network. To support CSFB signaling and Short Message Service (SMS) transfer for the UE102, the MME212may connect to the MSC server508. An SG interface510between the MSC server508and the MME212may enable the UE102to be both CS-registered and PS-registered while on the first network502. The SG interface510may be a reference point between the MME212and MSC server508. The SG interface510may used for the mobility management and paging procedures between PS domain and the CS domain. Paging messages may be exchanged via the SG interface510. Such paging messages may initiate the transition from hybrid voice and data to CSFB. Such paging messages may also initiate the transition from CSFB to hybrid voice and data.

As described in greater detail above, hybrid voice and data allows for simultaneous and/or concurrent communication of voice and data. In some configurations, the UE102may utilize a first communication link with a packet-switched network for communication of data, and the UE102may utilize a second communication link with a circuit-switched network for communication of data. The first communication link may exist concurrently and/or simultaneously with the second communication link. In other words, the second communication link may be a concurrent second communication link with the first communication link. Generally, a communication link may refer to a communication channel or path that connects two or more communicating devices. The communication link may provide one of many information transmission paths such as those of terrestrial radio communications. Without deviating from the scope of the present disclosure, the communication link may have various characteristics, such as point-to-point, broadcast, multipoint, point-to-multipoint, uplink, downlink, forward link, reverse link, or any other suitable characteristic(s). In some configurations, the UE102may utilize a first software stack for circuit-switched communication, such as voice service, and utilize a second software stack for packet-switched communication, such as data service. The first software stack may be utilized concurrently and/or simultaneously with the utilization of the second software stack. Generally, a software stack may refer to a series of protocols, codes, and/or instructions that can be implemented or executed by a processor of an apparatus (e.g., the UE102) to enable one or more functions, operations, aspects, and/or features. The software stack may sometimes be referred to as a protocol stack, or any other suitable term, without deviating from the scope of the present disclosure.

FIG. 6is a diagram600illustrating an example of coverage areas601-608,621-624associated with various networks. Such coverage areas601-608,621-624may sometimes be referred to as cellular regions or cells. Generally, a coverage area refers to a particular geographic region or boundary within which a transmitter may communicate with a receiver. Although the shapes of the coverage areas601-608,621-624illustrated inFIG. 6may appear to be relatively homogenous (e.g., hexagonal in shape), one of ordinary skill in the art will understand that the actual shapes of the coverage areas601-608,621-624may vary based on terrain, obstructions, and/or other various factors without deviating from the scope of the present disclosure. In the example illustrated inFIG. 6, each coverage area601-608,621-624defines the boundaries of a particular network node611-618,631-634, respectively. When the UE102is located within the coverage area601-608,621-624of the respective network node611-618,631-634, the network node611-618,631-634may communicate with the UE102. The network nodes611-618,631-634may refer to base stations, femto cells, home eNBs, pico cells, micro cells, macro eNB, low-power class eNBs, high-power class eNBs, and/or any other suitable apparatus configured for communication with the UE102. The network nodes611-618,631-634may be configured to provide access point to the EPC210and/or CS network230for the UEs102within its respective coverage area601-608,621-624. The network nodes611-618,631-634described herein may be associated with the networks502,504also described herein. For example, some network nodes631-634may be associated with the first network502(e.g., a network supporting hybrid voice and data), and some other network nodes611-618may be associated with the second network504(e.g., a network supporting CSFB without supporting hybrid voice and data). In some circumstances, the coverage areas of some network node(s) may overlap with the coverage areas of some other network node(s). For example, the coverage area623of a first network node633supporting hybrid voice and data may overlap with the coverage area607of a second network node617supporting CSFB without supporting hybrid voice and data. When the UE102is within both of the coverage areas607,623, the UE102may communicate with either or both of the network nodes617,633.

The UE102may roam from one location to another location. Generally, roaming may refer to any change in the coverage area associated with the UE102such that the UE102alters its selection of the network and/or network node with which it communicates. For example, the UE102may be physically moved by the user while walking, running, driving, flight, or any other suitable type of movement. However, one of ordinary skill in the art will understand that physical movement of the UE102is not a requirement of roaming. As mentioned above, roaming may refer to any change in the coverage area associated with the UE102such that the UE102alters its selection of the network and/or network node with which it communicates. For example, in some circumstances, even if the UE102is unmoved, the network and/or network node633may unexpectedly become inoperable and thus unable to communicate with the UE102. In such circumstances, the coverage area623of the network node633may no longer exist. This is a non-limiting example of a change in the coverage area associated with the UE102. Because the coverage area623of the network node633may no longer exist, the UE102may alter its selection of the network node with which it communicates. For example, the UE102may change its selection from a first network node633to a second network node617. The network nodes611-618,631-634may provide access to various types of networks, including networks the utilize technologies associated with 3G, 4G/LTE, 5G, and/or any other suitable communication protocol and/or standard.

FIG. 7is a diagram700illustrating an example of the UE102roaming from the coverage area associated with the first network502to a coverage area associated with the second network504. A non-limiting example of a network (e.g., network(s)502,504) is a public land mobile network (PLMN). Generally, a PLMN is a type of network that is established and/or operated by an administration or Recognized Operating Agency (ROA) for the purpose of providing land mobile telecommunication services to the public. A PLMN may provide communication services to the UE102. A PLMN may provide service in one or more frequency bands. A PLMN may be limited or bounded by the borders of a country. For example, the UE102may subscribe to services provided by an operator known as Verizon®. In the United States, Verizon® may have one or more PLMNs that support hybrid voice and data. If subscribed to Verizon®, the UE102can utilize hybrid voice and data while roaming in the United States. However, in Canada, operators may not have PLMNs that support hybrid voice and data. Accordingly, the UE102may not be able to utilize hybrid voice and data while roaming in Canada and, accordingly, may have to utilize CSFB. A country may have one or more PLMNs. A PLMN may be identified by the MCC and/or the Mobile Network Code (MNC). Each operator providing mobile services may have its own PLMN. One PLMN may interconnect with one or more other PLMNs, one or more Public Switched Telephone Networks (PSTNs) for telephone communications, and/or one or more Internet Service Providers (ISPs) for data and internet access. Access to the PLMN may be provided via an air interface between various apparatuses (e.g., UE102) and various network nodes (e.g., one or more of the network nodes611-618,631-634described above with reference toFIG. 6).

The coverage area associated with the first network502(e.g., first PLMN) may be limited to the boundaries of a first country702. The first network502(e.g., first PLMN) may provide support for hybrid voice and data. (This network502may also support CSFB, but hybrid voice and data may be preferred over CSFB because hybrid voice and data may provide a better user experience relative to CSFB.) The coverage area associated with the second network504(e.g., second PLMN) may be limited to the boundaries of a second country704(that is different from the first country702). The second network504(e.g., second PLMN) may not provide support for hybrid voice and data. However, the second network504(e.g., second PLMN) may provide support for other technologies, such as CSFB. As illustrated inFIG. 7, the UE102may roam from the coverage area associated with the first network502(e.g., first PLMN) to a second network504(e.g., second PLMN). In other words, the UE102may roam from a first coverage area that supports hybrid voice and data to a second coverage area that does not support hybrid voice and data (but does support CSFB).

After the UE102roams from a first coverage area that supports hybrid voice and data to a second coverage area that does not support hybrid voice and data (but does support CSFB), the UE102initiates system acquisition. Generally, system acquisition refers to a set of communication protocols implemented or utilized by the UE102for establishing a communication session with a particular cell, base station, network node, network (e.g., PLMN), etc. For example, a UE102initiating system acquisition to access an LTE network may follow a cell search procedure which includes a series of synchronization stages by which the UE102determines time and frequency parameters that are necessary for demodulating downlink signals, for transmitting with correct timing, and for acquiring critical system parameters. In LTE, such synchronization requirements may include symbol timing acquisition, carrier frequency synchronization, and sampling clock synchronization. System acquisition may also include searching for a PLMN that supports the type of communication preferred by the UE102. As described in greater detail above, such types of communication may include (i) hybrid voice and data and (ii) CSFB, wherein hybrid voice and data is preferred over CSFB by the UE102.

When a conventional UE roams from a first coverage area that supports hybrid voice and data to a second coverage area that does not support hybrid voice and data (but does support CSFB), the conventional UE will first search for a Home PLMN (HPLMN) before searching for any other type of PLMN. Generally, a PLMN is characterized as an HPLMN when the MCC and/or the MNC of the PLMN match the MCC and/or the MNC of the International Mobile Subscriber Identity (IMSI) stored on the SIM. In other words, a conventional UE will have the highest priority associated with the HPLMN relative to any other PLMN. Accordingly, during system acquisition, the conventional UE will first search the HPLMN before searching any other PLMN. However, in some circumstances, the conventional UE may not provide the fastest system acquisition possible. For instance, the conventional UE may roam from the coverage area associated with a first network (e.g., the HPLMN) that supports hybrid voice and data to the coverage areas of a second network (e.g., a Visited HPLMN (VPLMN), which may sometimes be referred to as a Roaming PLMN) that does not support hybrid voice and data (but does support CSFB). Generally, a VPLMN may refer to a PLMN that a UE visits after leaving its HPLMN. In such circumstances, the conventional UE will expend time and power to first search for the HPLMN, even though the conventional UE is no longer in the coverage area associated with the HPLMN. After expending time and power to search for the HPLMN, the conventional UE will terminate search for the HPLMN and, subsequently, begin searching for another PLMN (e.g., the VPLMN). Eventually, the conventional UE may succeed in system acquisition (e.g., of the VPLMN); however, the conventional UE will have needlessly expended time and power searching for the HPLMN.

In various aspects of the present disclosure, the UE102will not necessarily first search for the HPLMN. Firstly, the UE102detects roaming from the coverage area associated with the first network502(e.g., the HPLMN) providing coverage for hybrid voice and data to the coverage area associated with the second network (e.g., the VPLMN) that does not support hybrid voice and data (but does support CSFB). In some configurations, the UE102may detect that such roaming has occurred by: (i) comparing the information (e.g., an identifier, MCC, etc.) associated with the VPLMN with stored information (e.g., a list of identifiers, a list of MCC, etc.) associated with PLMNs that support hybrid voice and data, and (ii) determining that the UE102has roamed to a PLMN that is without support for the hybrid voice and data when that information (e.g., the identifier, the MCC, etc.) associated with the VPLMN does not match the stored information (e.g., the list of identifiers, the list of MCCs, etc.) associated with PLMNs that support hybrid voice and data. The foregoing is a non-limiting example of a technique that can be utilized for detecting the aforementioned roaming One of ordinary skill in the art will understand that the UE102can detect such roaming utilizing various techniques without deviating from the scope of the present disclosure.

Subsequently, the UE102may store data corresponding to the second network504(e.g., the VPLMN) such that the second network (e.g., the VPLMN) is set as a Registered PLMN (RPLMN). Generally, the RPLMN may refer to a PLMN for which the UE102has registered or performed a registration process. A non-limiting example of such data is system information associated with the second network (e.g., the VPLMN). Such information may be stored in a memory of the UE102(e.g., SIM module130of the memory114, as illustrated inFIG. 1). By storing system information associated with the second network (e.g., the VPLMN) in the memory of the UE102, the UE102can initiate system acquisition using this information even after being powered off (e.g., turned off). Storing of data for setting the VPLMN as the RPLMN may include adjusting the priority of the RPLMN to be higher than at least one other PLMN (e.g., the HPLMN). In some configurations, the UE102may switch communication from hybrid voice and data to CSFB after determining that the second network (e.g., the VPLMN) is without support for hybrid voice and data.

Afterwards, the UE102may initiate system acquisition. According to various aspects of the present disclosure, the system acquisition includes searching for the RPLMN prior to searching for any other PLMN. In comparison to the conventional UE described in greater detail above, the UE102searches for the RPLMN prior to searching for any other PLMN. For example, the UE102does not search for the HPLMN prior to searching for the RPLMN. In other words, the UE102searches for the second network504(supporting CSFB but without support for hybrid voice and data) before searching for the first network502(supporting hybrid voice and data). Because the UE102is no longer in the coverage area associated with the first network502(e.g., the coverage area associated with the HPLMN), the UE102does not needlessly expend time and power to search for the first network502(e.g., the HPLMN). Instead, the UE102first searches for the second network504(e.g., the VPLMN, which has been set as the RPLMN) for which the UE102is in its coverage area. Accordingly, under the roaming scenario described herein, the amount of time consumed by the UE102to perform system acquisition is less than the amount of time consumed by a conventional UE to perform system acquisition. In other words, the UE102is enabled to perform faster system acquisition relative to a conventional UE in certain circumstances.

FIG. 8is a diagram800illustrating an example of various methods and/or processes operable at the UE102. In some configurations, the methods and/or processes may be performed after the UE102is powered on (e.g., turned on). For example, referring toFIG. 7, the UE102may be powered on (e.g., turned on) after being moved from a first country702to a second country704. In some configurations, the methods and/or processes may be performed after the UE102has roamed from the coverage area associated with a first PLMN to the coverage area associated with a second PLMN. For example, referring toFIG. 7, the UE102roams from the coverage area associated with the first network502(e.g., the HPLMN) to the coverage area associated with the second network504(e.g., the VPLMN).

At block802, the UE102may compare information associated with the PLMN (e.g., a PLMN to which the UE102has roamed) with stored information associated with PLMNs that support hybrid voice and data. For example, the UE102may compare the MCC associated with the VPLMN with a list of MCCs associated with the PLMNs that support hybrid voice and data. If the information (e.g., the MCC) associated with the PLMN matches the stored information (e.g., the list of MCCs) associated with PLMNs that support hybrid voice and data, at block804, the UE102determines that the PLMN supports hybrid voice and data.

Alternatively, if the information associated with the PLMN does not match the stored information associated with PLMNs that support hybrid voice and data, at block806, the UE102determines that the PLMN is without support for hybrid voice and data. Accordingly, at block808, the UE102detects roaming from a coverage area associated with a first PLMN supporting hybrid voice and data to a coverage area associated with a second PLMN without support for hybrid voice and data (even though the second PLMN may provide support for CSFB). For example, referring toFIG. 7, the UE102detects roaming from the coverage area associated with the first network502(e.g., the HPLMN) supporting hybrid voice and data to the coverage area associated with the second network504(e.g., the VPLMN) without support for hybrid voice and data.

At block810, in response to the detection described above, the UE102may store data corresponding to the second PLMN such that the second PLMN is the RPLMN. An example of such information is system information associated with the second PLMN. Referring toFIG. 1, the UE102may store such information in the SIM module130of the memory114. As described in greater detail above, the RPLMN may have a higher priority relative to other PLMNs (e.g., the HPLMN) for purposes of PLMN search.

At block812, the UE102may switch communication from hybrid voice and data to CSFB after determining that the second PLMN is without support for hybrid voice and data. Because the UE102has determined that the second PLMN does not support hybrid voice and data, the UE102switches to CSFB, which is a technology that is supported by the second PLMN. Various aspects pertaining to CSFB and hybrid voice and data are described in greater detail above and therefore will not be repeated. The UE102may perform the switch from hybrid voice and data to CSFB utilizing various techniques without deviating from the scope of the present disclosure. For example, referring toFIG. 5, the UE102may utilize various signaling patterns and/or schemes involving the MME212, SGSN506, MSC server508, and/or SG interface510, which are described in greater detail above.

At block814, the UE102may initiate system acquisition, wherein the system acquisition includes searching for the RPLMN prior to searching for any other PLMN. Whereas a conventional UE will have needlessly expended time and power searching for the HPLMN prior to searching any other PLMN, the UE102searches for the RPLMN prior to searching any other PLMN (e.g., the HPLMN). In other words, the UE102does not search for the HPLMN prior to searching for the RPLMN. For example, referring toFIG. 7, the UE102searches for the second network504(supporting CSFB but without support for hybrid voice and data) before searching for the first network502(supporting hybrid voice and data). Because the UE102is no longer in the coverage area associated with the first network502(e.g., the coverage area associated with the HPLMN), the UE102does not needlessly expend time and power to search for the first network502(e.g., the HPLMN). Instead, the UE102first searches for the second network504(e.g., the VPLMN, which has been set as the RPLMN). Accordingly, under the roaming scenario described herein, the amount of time consumed by the UE102to perform system acquisition is less than the amount of time consumed by a conventional UE to perform system acquisition. In other words, the UE102is enabled to perform faster system acquisition relative to a conventional UE in certain circumstances.

The methods and/or processes described with reference toFIG. 8are provided for illustrative purposes and are not intended to limit the scope of the present disclosure. The methods and/or processes described with reference toFIG. 8may be performed in sequences different from those illustrated therein without deviating from the scope of the present disclosure. Additionally, some or all of the methods and/or processes described with reference toFIG. 8may be performed individually and/or together without deviating from the scope of the present disclosure. It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another—even if they do not directly physically touch each other. For instance, a first die may be coupled to a second die in a package even though the first die is never directly physically in contact with the second die. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure.