BACKGROUND:

Field:

Embodiments of the invention relate to supporting call continuity and/or ping-pong detection.

Description of the Related Art:

[0001] Long-term Evolution (LTE) is a standard for wireless communication that seeks to provide improved speed and capacity for wireless communications by using new modulation/signal processing techniques. The standard was proposed by the 3 ^rd Generation Partnership Project (3GPP), and is based upon previous network technologies, especially on Universal-Mobile-Telecommunications-System (UMTS). Since its inception, LTE has seen extensive deployment in a wide variety of contexts involving the communication of data.

SUMMARY:

[0002] According to a first embodiment, a method includes receiving, by a first network node, an indication that a call of a user equipment has been transferred from a first radio-access technology to a second radio-access technology. The method also includes storing, by the first network node, user-equipment context of the user equipment, upon receiving the indication.

[0003] In the method of the first embodiment, the receiving the indication comprises receiving an indication that the call of the user equipment has been transferred from Radio-Access-Network to Wi-Fi.

[0004] In the method of the first embodiment, the receiving by the first network node comprises receiving by a first base station.

[0005] In the method of the first embodiment, the receiving the indication comprises receiving the indication from the user equipment or from a Wi-Fi network.

[0006] According to a second embodiment, an apparatus may include at least one processor. The apparatus may also include at least one memory including computer program code. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to receive an indication that a call of a user equipment has been transferred from a first radio-access technology to a second radio-access technology. The apparatus may also be caused to store user-equipment context of the user equipment, upon receiving the indication.

[0007] In the apparatus of the second embodiment, the receiving the indication comprises receiving an indication that the call of the user equipment has been transferred from Radio- Access-Network to Wi-Fi.

[0008] In the apparatus of the second embodiment, the apparatus comprises a first base station.

[0009] In the apparatus of the second embodiment, the receiving the indication comprises receiving the indication from the user equipment or from a Wi-Fi network. [0010] According to a third embodiment, a computer program product may be embodied on a non-transitory computer readable medium. The computer program product may be configured to control a processor to perform a process including receiving, by a first network node, an indication that a call of a user equipment has been transferred from a first radio-access technology to a second radio-access technology. The process may also include storing, by the first network node, user- equipment context of the user equipment, upon receiving the indication.

[0011] According to a fourth embodiment, a method may include transmitting, by a user equipment, an indication that a call of the user equipment has been transferred from a first radio-access technology to a second radio-access technology. The indication is transmitted to a base station.

[0012] According to a fifth embodiment, an apparatus includes at least one processor. The apparatus includes at least one memory including computer program code. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to transmit an indication that a call of the apparatus has been transferred from a first radio-access technology to a second radio- access technology. The indication is transmitted to a base station.

[0013] According to a sixth embodiment, a computer program product may be embodied on a non-transitory computer readable medium. The computer program product may be configured to control a processor to perform a process including transmitting, by a user equipment, an indication that a call of the user equipment has been transferred from a first radio-access technology to a second radio-access technology. The indication is transmitted to a base station.

[0014] According to a seventh embodiment, a method may include receiving, by a first network node, an indication that a call of a user equipment comprises a call that was started in a first radio-access technology, shifted to a second radio-access technology, and shifted back to the first radio-access technology. The method may also include fetching, by the first network node, user-equipment context of a user equipment from a second network node, upon receiving the indication. The method may also include performing inter-radio-access-technology ping-pong detection using the fetched user-equipment context.

[0015] In the method of the seventh embodiment, the first and the second network nodes correspond to the same node. [0016] In the method of the seventh embodiment, the receiving comprises receiving an indication that a call was started in Radio- Access-Network and shifted to Wi-Fi.

[0017] In the method of the seventh embodiment, the first network node comprises a first base station, and the second network node comprises a second base station.

[0018] In the method of the seventh embodiment, receiving the indication comprises receiving the indication from the user equipment via Radio-Resource-Control signaling or via an enhancement to user-equipment-based history information.

[0019] In the method of the seventh embodiment, the enhancement comprises information relating to where the call started.

[0020] According to an eighth embodiment, an apparatus includes at least one processor. The apparatus also includes at least one memory including computer program code. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to receive an indication that a call of a user equipment comprises a call that was started in a first radio-access technology, shifted to a second radio-access technology, and shifted back to the first radio-access technology. The apparatus may also be caused to fetch user- equipment context of a user equipment from a network node, upon receiving the indication. The apparatus may also be caused to perform inter-radio-access- technology ping-pong detection using the fetched user-equipment context.

[0021] In the apparatus of the eighth embodiment, the first and the second network nodes correspond to the same node.

[0022] In the apparatus of the eighth embodiment, the receiving comprises receiving an indication that a call was started in Radio- Access-Network and shifted to Wi-Fi. [0023] In the apparatus of the eighth embodiment, the apparatus comprises a first base station, and the network node comprises a second base station.

[0024] In the apparatus of the eighth embodiment, receiving the indication comprises receiving the indication from the user equipment via Radio-Resource-Control signaling or via an enhancement to user-equipment-based history information.

[0025] In the apparatus of the eighth embodiment, the enhancement comprises information relating to where the call started.

[0026] According to a ninth embodiment, a computer program product, may be embodied on a non-transitory computer readable medium. The computer program product may be configured to control a processor to perform a process including receiving, by a first network node, an indication that a call of a user equipment comprises a call that was started in a first radio-access technology, shifted to a second radio-access technology, and shifted back to the first radio-access technology. The process may also include fetching, by the first network node, user-equipment context of a user equipment from a second network node, upon receiving the indication. The process may also include performing inter-radio-access-technology ping-pong detection using the fetched user-equipment context.

BRIEF DESCRIPTION OF THE DRAWINGS: [0027] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[0028] Fig. 1 illustrates an example procedure performed by certain embodiments of the present invention.

[0029] Fig. 2 illustrates a flow diagram of a method according to one embodiment. [0030] Fig. 3 illustrates a flow diagram of another method according to one embodiment. [0031] Fig. 4 illustrates a flow diagram of another method according to one embodiment.

[0032] Fig. 5 illustrates an apparatus in accordance with one embodiment.

[0033] Fig. 6 illustrates an apparatus in accordance with another embodiment.

[0034] Fig. 7 illustrates an apparatus in accordance with another embodiment.

[0035] Fig. 8 illustrates an apparatus in accordance with another embodiment.

DETAILED DESCRIPTION:

[0036] Embodiments of the present invention are directed to supporting call continuity and/or ping-pong detection. Certain embodiments may support call continuity and ping-pong detection in a 3GPP Radio-Access-Network and/or Wi-Fi environment.

[0037] Because an increasing amount of an operator's traffic is being rationed to data traffic, and because a Wi-Fi interface is generally available in most smartphones, operators look toward Wi-Fi resources as a supplementary capacity for offering services. In order to use Wi-Fi as a supplementary capacity for offered services, such use may require an increased amount of coordination between 3GPP technologies and Wi-Fi technologies. The study item "Multi-RAT Join Coordination SI" was formed to analyze the scope and means of possible cooperation between 3GPP technologies and Wi-Fi technologies. This study item addresses whether any information exchange between 3GPP RAN (and, in particular, 3GPP LTE technologies) and Wi-Fi is necessary. If information exchange is necessary, the study item addresses an appropriate method to transfer the necessary information.

[0038] One of the difficulties relating to interaction between 3GPP RAN technologies and Wi-Fi technologies relates to the preservation of call continuity. If a call is started in the 3 GPP RAN, then transferred to Wi-Fi, and then shifted back to the 3 GPP RAN, the call will be perceived differently from the user's perspective as compared to the network's perspective. From the perspective of the user, the call is a single, continuous call. From the perspective of the network, a connection of the call first ends when the user equipment (UE) switches to Wi-Fi, and a new connection for the call starts once the UE moves back to the 3 GPP RAN. In between the end of the first connection and the beginning of the new connection, the UE is in an idle mode (assuming a single Access Point Name (APN) connection). Off-loading is assumed to be performed with APN granularity.

[0039] In view of the above, two consequences may result. With a first consequence, possible inter-Radio-Access-Technology (inter-RAT) ping-pongs may not be detectable. UE history information generally does not include information relating to the amount of time that a UE stays in Wi-Fi. With a second consequence, Quality-of- Service (QoS) at a 3GPP RAN may be provided only based on core-network mechanisms. For Evolved-UMTS-Terrestrial-Radio- Access-Network (E-UTRAN), there is generally no relation between the first and the second calls.

[0040] The problem of maintaining call continuity between 3GPP RAN/GSM-Edge- Radio-Access-Network (GERAN) technologies and Wi-Fi (or any other Radio- Access-Technology (RAT)) has not been addressed by the previous approaches. However, some existing mechanisms, which were created for other purposes, can be reused to address the problem of maintaining/providing call continuity. For example, UE History Information was created for the purpose of identifying ping-pong cases within LTE cells, within UTRAN cells, and between the cells of these two RATs. UE History Information requires, however, that the UE context is transferred from a source to a target (such as from a source evolved Node B (eNB) to a target evolved Node B), which is currently not possible when the UE moves between RAN and Wi- Fi. The mechanism also includes inter-eNB reporting of detected inter-RAT ping- pongs, existing in LTE. The inter-eNB reporting of detected inter-RAT ping-pongs, however, generally requires continuity of history recording. Another existing mechanism is UE-based idle history information. UE-based idle history information is the same as the above-described UE History Information, but UE-based idle history information is recorded at the UE. The difference between UE History Information and UE-based idle history information is that, with UE-based idle history information, the UE also records the cells that the UE is camped on while in the idle state. The UE also records the time outside of LTE coverage. The purpose served by UE-based idle history information is, however, to enable better assessment of UE mobility, and not to enable ping-pong detection.

[0041] In addition to the above-described mechanisms, another existing mechanism is Context fetch. Context fetch is an implementation-based solution which enables transferring of UE context to a cell at which the UE reconnects after a failure. Normally, if the cell is not prepared, the UE would be rejected and the call would be dropped. The context fetch enables the saving of call continuity. Context fetch increases mobility robustness in heterogeneous networks (HetNets) and small cell environments.

[0042] Certain embodiments of the present invention combine the above-described mechanisms so that call continuity (and therefore, ping-pong detection, for example) are enabled/provided in the RAN- Wi-Fi environment. Wi-Fi is mentioned as one possible radio-access technology that is used by certain embodiments of the present invention. Other embodiments of the present invention may use other types of radio- access technologies (such as, for example, WiMAX and/or high-rate -packet-data technologies). To achieve call continuity (and ping-pong detection), the following elements are provided. First, an original controller node (such as a base- station/eNB/Radio-Network-Controller(RNC)) stores UE context when a call is transferred to Wi-Fi. A subsequent controller node (a second base-station/eNB/RNC) is aware that the call was started in RAN and the particular node that has stored the UE context. The subsequent controller node (the second base-station/eNB/RNC) is able to fetch the UE context from the first controller node.

[0043] If the above elements are provided, the second controller node will have the information that the second controller node would normally have, if the second controller were to be a handover target. Because the second controller node has this information, at least, inter-RAT ping-pong detection is enabled, as described in more detail below. If further enhancements are considered at the EUTRAN-Radio-Access- Bearer (E-RAB) connection setup, the E-RAB connection setup may also allow setting the E-RAB QoS to the same values as in the first call. [0044] Certain embodiments of the present invention design new signalling or enhance an existing signalling. With regard to context storing, when a call is transferred to Wi-Fi, the decision for context storing is generally based on evaluation of pre-set conditions at the UE. According to the previous approaches, the serving eNB/RNC is generally not aware that the call has been transferred to Wi-Fi. As such, according to the previous approaches, from the RAN perspective, the call simply ends.

[0045] In contrast to the previous approaches, certain embodiments of the present invention inform the serving eNB/RNC that the UE has been transferred to Wi-Fi. As such, certain embodiments of the present invention enable the storing of context for future fetching. The information indication regarding the transfer to Wi-Fi may come either from the UE itself (as an enhancement in Radio-Resource-Control signalling) or from Wi-Fi (as a Wi-Fi-RAN information exchange), or from other network elements that are aware that the UE moved to Wi-Fi such as, for example, a Wi-Fi authorization server. Another alternative is to store all UE contexts after calls end. The time that the context should be stored can vary based upon implementation (as a reference, the time for storing UE context for Mobility-Robustness-Optimization (MRO) purposes is 48 hours).

[0046] With regard to call continuity awareness, if the UE returns from Wi-Fi back to 3GPP RAN, the eNB/RNC (to which the UE returns to) perceives the call setup, and the eNB/RNC is typically unaware that the call is a continuation of a previous call (the eNB/RNC considers the call to be a new call). The eNB/RNC considers the call as a traffic shift from Wi-Fi. In order to let the eNB/RNC know that the call is actually a continuation of a call started in RAN and then shifted to Wi-Fi, an indication of the continuation is transmitted from the UE. Such an indication may be enabled by an enhancement in RRC signalling, either in a form of a new indicator or as an enhancement to the existing UE-based idle history information. The enhancement may contain information where the call started (information such as a EUTRAN-Cell- Global-Identifier (ECGI) and/or Tracking-Area-Identifier (TAI)).

[0047] With regard to Context fetching, based on the indication from the UE, the eNB/ adio-Network-Controller (to which the UE returns to) will fetch the context. According to the previous approaches, this fetching may be achieved using existing signalling (Radio-link-failure (RLF) INDICATION and Handover (HO) REQUEST). RLF INDICATION is a message that reports connection failure. However, if RLF INDICATION is to be reused, it may trigger MRO actions, even though no failure occurred.

[0048] In view of the above difficulties, certain embodiments of the present invention provide a new inter-controller (e.g., X2/S1 or Iu/Iur) signalling. The new signalling enables fetching of the context stored at the eNB/RNC (the eNB/RNC from which the UE moved away from to Wi-Fi). In response, UE context information may be transferred. The UE context information may be information related to the connection before the UE moved to WiFi, i.e., the connection to the first/original eNB/RNC. The UE context information may include UE history information and/or Quality-of- Service (QoS) settings. The response may be based on a HO REQUEST (possibly with some enhancements or simplification - some parts of regular HO REQUEST may not be needed, for example, Access-Stratum (AS) security), but also a new message may be defined. [0049] With regard to utilization of the context information, based on the information relating to the time the UE stayed in Wi-Fi, the eNB/RNC (to which the UE returns to) may indicate to the original eNB/RNC that a UE (that was served by the original eNB/RNC) was offloaded to Wi-Fi and then immediately shifted back to LTE. Embodiments of the present invention can provide this indication via a same message that was used for LTE-3G ping-pong (HO REPORT), with small enhancements. Another possibility for providing this indication is via the E-RAB list and associated QoS information when the new E-RABs are set up. This option would include enhancements in the initial E-RAB setup procedure. Other applications for utilizing the context information may arise in the future, as UMTS/LTE/Wi-Fi integration continues.

[0050] Fig. 1 illustrates an example procedure of one embodiment of the present invention. The term "UE context" refers to a set of parameters that are specific for a particular connection of a particular UE. The exact content of UE context may vary depending on the actual scenario that the UE context is applied to.

[0051] If the ping-pong detection is the only scenario for which the UE context is applied to, then the context may be limited to the UE History Information. In this case, if the indication from the UE about call continuity contains all the information needed to detect the inter-RAT ping-pong (for example, the information relating to the time the UE stayed at Wi-Fi), the context fetch may not be necessary. In LTE, the receiving eNB may directly notify the source eNB about the problem using existing X2 signalling. [0052] If the E-RAB setup procedure over SI is enhanced so that the previously used QoS parameters may be transferred to the Mobility-Management-Entity (MME), then the list of E-RABs, together with their configurations, should be a part of the stored UE context as well.

[0053] If the Wi-Fi coverage is always within a single LTE/UMTS cell, then inter- controller signalling may not be needed because the original controller and the second controller are the same node.

[0054] Fig. 2 illustrates a logic flow diagram of a method according to certain embodiments of the invention. The method illustrated in Fig. 2 includes, at 210, receiving, by a first network node, an indication that a call of a user equipment has been transferred from a first radio-access technology to a second radio-access technology. The method also includes, at 220, storing, by the first network node, user- equipment context of the user equipment, upon receiving the indication.

[0055] Fig. 3 illustrates a logic flow diagram of a method according to certain embodiments of the invention. The method illustrated in Fig. 3 includes, at 310, receiving, by a first network node, an indication that a call of a user equipment comprises a call that was started in a first radio-access technology, shifted to a second radio-access technology, and shifted back to the first radio-access technology. The method includes, at 320, fetching, by the first network node, user-equipment context of a user equipment from a second network node, upon receiving the indication. The method includes, at 330, performing inter-radio-access-technology ping-pong detection using the fetched user-equipment context. [0056] Fig. 4 illustrates a logic flow diagram of a method according to certain embodiments of the invention. The method illustrated in Fig. 4 includes, at 410, transmitting, by a user equipment, an indication that a call of the user equipment has been transferred from a first radio-access technology to a second radio-access technology, wherein the indication is transmitted to a base station. The method may also include, at 420, transmitting user-equipment context to the base station.

[0057] Fig. 5 illustrates an apparatus in accordance with one embodiment. Apparatus 500 includes a receiving unit 510 that receives an indication that a call of a user equipment has been transferred from a first radio-access technology to a second radio- access technology. Apparatus 500 also includes a storing unit 520 that stores user- equipment context of the user equipment, upon receiving the indication.

[0058] Fig. 6 illustrates an apparatus in accordance with one embodiment. The apparatus 600 includes a receiving unit 610 that receives an indication that a call of a user equipment comprises a call that was started in a first radio-access technology, shifted to a second radio-access technology, and shifted back to the first radio-access technology. The apparatus 600 also includes a fetching unit 620 that fetches user- equipment context of a user equipment from a network node, upon receiving the indication. The apparatus 600 also includes a performing unit 630 that performs inter- radio-access-technology ping-pong detection using the fetched user-equipment context.

[0059] Fig. 7 illustrates an apparatus in accordance with one embodiment. The apparatus 700 includes a first transmitting unit 710 that transmits an indication that a call of the apparatus has been transferred from a first radio-access technology to a second radio-access technology. The indication is transmitted to a base station. The apparatus 700 may also include a second transmitting unit 720 that transmits user- equipment context to the base station.

[0060] Fig. 8 illustrates an apparatus 10 according to embodiments of the invention. Apparatus 10 can be a device, such as a UE, for example. In other embodiments, apparatus 10 can be a base station, access point, and/or an eNB, for example.

[0061] Apparatus 10 can include a processor 22 for processing information and executing instructions or operations. Processor 22 can be any type of general or specific purpose processor. While a single processor 22 is shown in Fig. 8, multiple processors can be utilized according to other embodiments. Processor 22 can also include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples.

[0062] Apparatus 10 can further include a memory 14, coupled to processor 22, for storing information and instructions that can be executed by processor 22. Memory 14 can be one or more memories and of any type suitable to the local application environment, and can be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. For example, memory 14 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 can include program instructions or computer program code that, when executed by processor 22, enable the apparatus 10 to perform tasks as described herein.

[0063] Apparatus 10 can also include one or more antennas (not shown) for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 can further include a transceiver 28 that modulates information on to a carrier waveform for transmission by the antenna(s) and demodulates information received via the antenna(s) for further processing by other elements of apparatus 10. In other embodiments, transceiver 28 can be capable of transmitting and receiving signals or data directly.

[0064] Processor 22 can perform functions associated with the operation of apparatus 10 including, without limitation, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes related to management of communication resources.

[0065] In certain embodiments, memory 14 stores software modules that provide functionality when executed by processor 22. The modules can include an operating system 15 that provides operating system functionality for apparatus 10. The memory can also store one or more functional modules 18, such as an application or program, to provide additional functionality for apparatus 10. The components of apparatus 10 can be implemented in hardware, or as any suitable combination of hardware and software. [0066] The described features, advantages, and characteristics of the invention can be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages can be recognized in certain embodiments that may not be present in all embodiments of the invention. One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.