DESC:FIELD OF THE INVENTION
The present invention generally relates to wireless communications technology and more particularly to a method and system for enabling call session continuity between Vo-WiFi and circuit switched domains.

BACKGROUND OF THE INVENTION
Vo-WiFi (Voice over Wireless Fidelity) is generally a WiFi based (VOIP) Voice over internet protocol service. Where VOIP consists of hardware and software that enable people to use the internet as the transmission medium for telephone calls. Vo-WiFi utilizes IMS (IP multimedia system) technology to provide a packet voice service that is delivered over IP via WiFi network and is designed to work on wireless devices such as laptops, tablets, Personal digital Assistants(PDA), smartphones, etc. Vo-WiFi allows a UE to switch to WIFI to make voice calls instead of using the cellular network.

Several mobile network operators provide Vo-WiFi service which is beneficial to users who have poor residential cellular coverage. For example, the devices first connect via the WiFi access point in the user’s homes and then connect automatically to the network operator provided voice service. Users can enjoy voice and video calling (if supported by the specific device), and seamless handover of ongoing voice calls is enabled between Long Term Evolution (LTE) and WiFi networks, if the network operator has launched Voice over LTE (VoLTE). However, in case of network operators such as BSNL, Sprint, Claro, MTS etc., supports only Vo-WiFi and not VoLTE. Therefore, there is a chance of Vo-WiFi call drop, if the user moves out of WiFi coverage area.

The Vo-WiFi call is dropped for various other reasons such as
1. If a mobile network operator (MNO) of the mobile terminals does not support VoLTE.
2. If the mobile terminals are not latched to LTE.
3. If an IMS registration over LTE fails during a VoLTE call between the first and second mobile terminal.

In view of the foregoing, there exists a need to provide a method and system which enables call continuity between Vo-WiFi and circuit switched domains when the user moves out of WiFi coverage and the operator does not support VoLTE.

The above-mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

Figure 1 is a schematic diagram illustrating a method for call continuity between VoWiFi and circuit switched call, according to an embodiment of the present invention.

Figure 2 is a schematic diagram illustrating call state change procedure, according to an embodiment of the present invention.

Figure 3 is a schematic flow diagram illustrating a scenario of placing multiple call between same identities, according to an embodiment of the present invention.

Figure 4 illustrates a scenario of Vo-WiFi call user moving out of WLAN vicinity, according to an embodiment of the present invention.

Figure 5 illustrates a scenario when a user moves into a WLAN vicinity during a CS call, according to an embodiment of the present invention.

Although specific features of the present invention are shown in some drawings and not in others, this is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

SUMMARY OF THE INVENTION
Various embodiments of the present invention herein describe a method of enabling call continuity by switching a call between a Voice over-WiFi (VoWiFi) network and a Circuit switched (CS) network. The method of comprises of initiating the call over a VoWiFi network between a first user equipment and a second user equipment, switching the call, between the first User Equipment (UE1) and the second User Equipment (UE2), from the VoWiFi network to the circuit switched network in background without user intervention, when the Wi-Fi signal strength drops below a predefined threshold value and VoWiFi to -VoLTE (Voice over Long-Term Evolution) handover is unfeasible, thereby enabling the call continuity by switching the call between the VoWiFi network and the Circuit switched network.

According to an embodiment of the present invention, the method further comprises of switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network in the background without user intervention, when the Wi-Fi signal strength increases above the predefined threshold value.

According to an another embodiment of the present invention, the method further comprises of switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network without user intervention, when the IMS registration over WLAN is successful.

According to an embodiment of the present invention, wherein the circuit switched (CS) call comprises one of a voice call, video call and P2P session between the UE 1 and the UE 2.

In another embodiment of the present invention, wherein switching the call from the VoWiFi network to the circuit switched network further based on at least one of a mobile network operator fails to support the VoLTE, the UE1 fails to latch on the VoLTE and the UE1 fails to register on Internet Protocol (IP) Multimedia Subsystem (IMS) over the VoLTE.

According to an embodiment of the present invention, wherein switching the call between the VoWiFi network and the Circuit switched (CS) network while having same identity of a mobile originator (MO) and mobile terminator (MT), as in active call.

According to an embodiment of the present invention, the method further comprises of sending a message to one of the UE1 and UE 2 with a reason for disconnection on loosing Wi-Fi bearer if one of a Packet Switched (PS) call and Circuit Switched (CS) call is not connected.

According to another embodiment of the present invention, wherein the call over VoWiFi includes a call over one of an unsecured Wi-Fi bearer and secured Wi-Fi bearer.

In yet another embodiment of the present invention, the method further comprises of handling a second call in UE comprising steps of receiving, by the UE2, one or more subsequent calls in a row from the UE1 having an identity identical to the identity of the UE1 during the active call, placing, by the UE2, the active call on hold, accepting a recent subsequent call from the one or more subsequent calls and disconnecting the active call placed on hold without user intervention.

According to an embodiment of the present invention, the method further comprises of handling a second call in UE comprising steps of receiving, by the UE2, one or more subsequent calls in a row from the UE1 having an identity identical to the identity of the UE1 during the active call, disconnecting the active first call and accepting a recent subsequent call from the one or more subsequent calls without user intervention.

According to an embodiment of the present invention, the method further comprises of preempting, by a network; a previous call session and establishing later call session without call state notifications to the UE1 and UE2, when multiple calls are made between UE1 and UE2.

In another embodiment of the present invention, wherein switching the call, between the first User Equipment (UE1) and the second User Equipment (UE2), from the VoWiFi network to the circuit switched network when a user is moving out of WLAN vicinity during a call over the VoWiFi network comprises steps of moving by the UE1 during the active call over VoWiFi, out of the WLAN vicinity, evaluating, by the UE1, possibility of the call handover to the VoLTE and deduced handover, placing by the UE1, the call on the Circuit switch network in the background and offload the call and establishing the call on the circuit switch network between the UE1 and the UE2.

According to an embodiment of the present invention, wherein switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network when the user is moving into a WLAN vicinity during the call over circuit switched network, comprises steps of establishing, the call over circuit switched network between the UE1 and the UE2, moving by the UE1 into the WLAN vicinity, establishing session with IMS PDN and IMS registration upon moving into WLAN vicinity, placing by the UE1, the call over VoWiFi network to the UE2 in the background and offloading the call and initiating the call over the VoWiFi network when UE1 is present in the WLAN vicinity.

The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understand the more complete detailed description which is to follow. In reference to such, there is to be a clear understanding that the present invention is not limited to the method or application of use described and illustrated herein. It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method and system for enabling call session continuity between Vo-WiFi and circuit switched domains. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The embodiments herein and the various features and advantages details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

The present invention discloses a method and system for call continuity between VoWiFi and circuit switched domains. According to the present invention, when Wi-Fi signal strength drops below a threshold value and VoWiFi -VoLTE handover is not possible, a circuit switched call to the other party is placed in the background. Further, When Wi-Fi signal strength gains above a threshold value, an IMS session is established and VoWiFi call to the other party is placed in the background. Furthermore, when a user of first mobile terminal is already in Vo WiFi call and a normal CS call is established by second mobile terminal then, the system detects the call is from same identity, preempts the active call and accepts the incoming CS call without user’s intervention.

Figure 1 is a schematic diagram illustrating a method for call continuity between VoWiFi and circuit switched call, according to an embodiment of the present invention. A Vo-WiFi call (106) is initiated at a first mobile terminal (102) and sent through an ePDG (Evolved Packet Data Gateway) (104) to a second mobile terminal (108). The ePDG secures the data transmission with the mobile terminals connected to an EPC (evolved packet core) over an untrusted Wi-Fi access.

The present invention enables placing a circuit switched call (110) during an active Vo-WiFi call (106) without user intervention and allows to place a Vo-WiFi call (106) during an active circuit switched call (110) without user intervention, when the handover to Vo-LTE is not possible.

Further, during a VoWiFi call (106), decision to place a circuit switched call (110) instead of handover to VoLTE call is made, if a mobile network operator (MNO) of the mobile terminals does not support VoLTE (or) if the mobile terminals are not latched to LTE (or) if a IMS registration over LTE fails during a VoLTE call between the first and second mobile terminal. Similarly, during a circuit switching call (110), decision to place a VoWiFi call (106) is made if a good WLAN signal strength is available and if a IMS registration over WLAN is possible.

Figure 2 is a schematic diagram illustrating a Call state change procedure, according to an embodiment of the present invention. Decision to Call state change (Vo-WiFi to CS call (or) CS call to Vo-WiFi call) is done to enable call session continuity between Vo-WiFi and circuit switched domains. During a VoWiFi call (106), decision to place a circuit switched call (110) is made if a mobile network operator (MNO) of the mobile terminals does not support VoLTE (or) if the mobile terminals are not latched to LTE (or) if a IMS registration over LTE fails during a VoLTE call between the first and second mobile terminal.

Similarly, during a circuit switching call (110), decision to place a VoWiFi call (106) is made if a good WLAN signal strength is available and if a IMS registration over WLAN is possible.

In an embodiment, during a call state change between CS call (110) and Vo -WiFi call (106), an RIL 204 (radio interface layer) provides an interface that handles the call state changes between circuit switched (CS) call (110) and Vo-WiFi call (106). The call state changes are not notified to an application layer (202) during call offloading between same mobile numbers/identities, so that user’s call is continued without his/her intervention.

Figure 3 is a schematic flow diagram illustrating a scenario of placing multiple calls between same identities, according to an embodiment of the present invention. According to the flow diagram, at step 1, first mobile terminal and second mobile terminal are already indulged in Vo-WiFi active call. At step 2, the first mobile terminal establishes a circuit switching call to the second mobile terminal. At step 3, core network element identifies if the call is from same identity or not. At step 4, the core element identifies that the call is from same identity from which the Vo-WiFi active call was established to second terminal and the network element preempts the previous active Vo-WiFi call session and establishes later CS call session with or without User intervention. Finally, at step 5, an active CS call is established with later call session.

According to the embodiment of the present invention disclosed in Figure 3, if there are consecutive calls made between same mobile operator (MO) and mobile terminal (MT) identities, then the network terminates the previous call and establishes the later call without sending call state notifications to the mobile terminals.

Figure 4 illustrates a scenario of a first mobile terminal user (102) in a Vo-WiFi call moving out of WLAN (402) vicinity, according to an embodiment of the present invention. According to the scenario, at step 1, the first mobile terminal user (102) is on Vo-WiFi call and is present within WLAN vicinity and, second mobile terminal user 108 core network is immaterial as no call is established. At step 2, the first mobile terminal user (102) moves out of WLAN vicinity and is about to hit WLAN signal strength threshold value for handover. When it hits the threshold value then, the first mobile terminal user (102) evaluates the possibility of call handover to VoLTE. The deduced handover is not possible if a mobile network operator (MNO) of the mobile terminals does not support VoLTE (or) if the mobile terminals are not latched to LTE (or) if a IMS registration over LTE fails during a VoLTE call between the first and second mobile terminal. Therefore, at step 3, a circuit switched call is established to the second mobile terminal (108) in background and call is offloaded.

Figure 5 illustrates a scenario when a first mobile terminal user (102) moves into a WLAN vicinity during a CS call with second mobile terminal (108), according to an embodiment of the present invention. According to this scenario, at step 1, a first mobile terminal user (102) is already in a CS call with a second mobile terminal (108). At step 2, a first mobile terminal user (102) moves into WLAN vicinity. The first mobile terminal user (102) detects the WLAN signal strength is above a threshold value and evaluates the possibility of call handover.

Next, the first mobile terminal establishes a session with IMS PDN and IMS registration is done. Now that the IMS registration is done, the first mobile terminal can place a VoWiFi call to the second mobile terminal in the background and offloads the call.

Thus, the present invention enables call continuity between Vo-WiFi and circuit switched domains when the user moves out of WiFi coverage and the operator does not support VoLTE.

In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

,CLAIMS:We Claim:

1. A method of enabling call continuity by switching a call between a Voice over- WiFi (VoWiFi) network and a Circuit switched (CS) network comprising:
initiating the call over a VoWiFi network between a first user equipment and a second user equipment;
switching the call, between the first User Equipment (UE1) and the second User Equipment (UE2), from the VoWiFi network to the circuit switched network, when the Wi-Fi signal strength drops below a predefined threshold value and VoWiFi to -VoLTE (Voice over Long-Term Evolution) handover is unfeasible, thereby enabling the call continuity by switching the call from the VoWiFi network to the Circuit switched network.

2. The method as claimed in claim 1, wherein switching the call, between the first User Equipment (UE1) and the second User Equipment (UE2), from the VoWiFi network to the circuit switched network is performed in background without user intervention.

3. The method as claimed in claim 1 further comprising switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network in the background without user intervention, when the Wi-Fi signal strength increases above the predefined threshold value.

4. The method as claimed in claim 3 further comprising switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network without user intervention, when the IMS registration over WLAN is successful.

5. The method as claimed in claim 1, wherein the circuit switched (CS) call comprises one of a voice call, video call and P2P session between the UE 1 and the UE 2.

6. The method as claimed in claim 1, wherein switching the call from the VoWiFi network to the circuit switched network further based on at least one of a
mobile network operator fails to support the VoLTE;
the UE1 fails to latch on the VoLTE; and
the UE1 fails to register on Internet Protocol (IP) Multimedia Subsystem (IMS) over the VoLTE.

7. The method as claimed in claim 1, wherein switching the call between the VoWiFi network and the Circuit switched (CS) network while having same identity of a mobile originator (MO) and mobile terminator (MT), as in active call.

8. The method of claim 1 further comprising sending a message to one of the UE1 and UE 2 with a reason for disconnection on loosing Wi-Fi bearer if one of a Packet Switched (PS) call and Circuit Switched (CS) call is not connected.

9. The method of claim 1, wherein the call over VoWiFi includes a call over one of an unsecured Wi-Fi bearer and secured Wi-Fi bearer.

10. The method of claim 1 further comprising handling a second call in UE comprising steps of:
receiving, by the UE2, one or more subsequent calls in a row from the UE1 having an identity identical to the identity of the UE1 during the active call;
placing, by the UE2, the active call on hold;
accepting a recent subsequent call from the one or more subsequent calls; and
disconnecting the active call placed on hold without user intervention.

11. The method of claim 1 further comprising handling a second call in UE comprising steps of:
receiving, by the UE2, one or more subsequent calls in a row from the UE1 having an identity identical to the identity of the UE1 during the active call;
disconnecting the active first call; and
accepting a recent subsequent call from the one or more subsequent calls without user intervention.

12. The method of claim 1 further comprising:
preempting, by a network; a previous call session and establishing later call session without call state notifications to the UE1 and UE2, when multiple calls are made between UE1 and UE2.

13. The method of claim 1, wherein switching the call, between the first User Equipment (UE1) and the second User Equipment (UE2), from the VoWiFi network to the circuit switched network when a user is moving out of WLAN vicinity during a call over the VoWiFi network comprises steps of:
moving by the UE1 during the active call over VoWiFi, out of the WLAN vicinity;
evaluating, by the UE1, possibility of the call handover to the VoLTE and deduced handover;
placing by the UE1, the call on the Circuit switch network in the background and offload the call; and
establishing the call on the circuit switch network between the UE1 and the UE2.

14. The method of claim 3, wherein switching the call, between the UE1 and the UE2, from the circuit switched network to the VoWiFi network when the user is moving into a WLAN vicinity during the call over circuit switched network, comprises steps of:
establishing, the call over circuit switched network between the UE1 and the UE2;
moving by the UE1 into the WLAN vicinity;
establishing session with IMS PDN and IMS registration upon moving into WLAN vicinity;
placing by the UE1, the call over VoWiFi network to the UE2 in the background and offloading the call; and
initiating the call over the VoWiFi network when UE1 is present in the WLAN vicinity.

Dated this the 15th day of May 2018

Signature

Birendra Kumar
Patent agent (IN PA 1102)
Agent for the applicant