CLIAMS:
1. A method for handling inter-domain handover of voice call from voice over long term evolution (VoLTE) to circuit switched (CS) domain in dual radio user equipment (UE), the method comprises of:
sending, by the UE, an ATTACH/ TRACKING AREA UPDATE request along with a simultaneous GSM and LTE (SGLTE) Dual radio capability information to a Mobile Management Entity (MME);
sending, by the UE, a cell identity (ID) of current registered CS RAT to an eNodeB when Voice call in LTE (VoLTE Call) needs to be continued over CS RAT(2G/3G);
sending, by the eNodeB, a handover request comprising a target cell ID and a voice call continuity indication to the MME;
validating, by the MME, whether the UE is SGLTE capable by verifying the voice call continuity indication;
receiving, by a Mobile Switching Centre (MSC), the handover request transmitted from the MME if the UE is SGLTE capable;
providing, by the MSC, the handover request from the MME to the target CS RAT; and
switching, by the UE, from the VoLTE RAT to the CS RAT for continuing the voice call.

2. The method of claim 1, wherein the handover request comprises at least one of:
International mobile subscriber Identity (IMSI) of the UE;
Identity information of the target CS RAT;
Session Transfer Number (STN-SR);
Correlation Mobile Station ISDN number (C-MSISDN); and
SGLTE bit.

3. The method of claim 1, wherein the UE informs the SGLTE capability to the network by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request.

4. The method of claim 1, wherein the UE informs the network that UE supports Voice Call handover by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request.

5. A system for handling inter-domain handover of voice call from voice over long term evolution (VoLTE) to circuit switched (CS) domain, the system comprising:
a dual radio User Equipment (UE) adapted for:
sending an ATTACH/ TRACKING AREA UPDATE request along with a simultaneous GSM and LTE (SGLTE) Dual radio capability information to a Mobile Management Entity (MME);
sending a cell identity (ID) of current registered CS RAT to an eNodeB when Voice call in LTE (VoLTE Call) needs to be continued over CS RAT(2G/3G);
an eNode B adapted for:
sending a handover request comprising a target cell ID and a voice call continuity indication to the MME;
a Mobile Switching Centre (MSC) adapted for:
receiving the handover request transmitted from the MME if the UE is SGLTE capable; and
providing, by the MSC, the handover request from the MME to the target CS RAT.

6. The system of claim 5, wherein the UE is further adapted for switching from the VoLTE RAT to the CS RAT for continuing the voice call. ,TagSPECI:FIELD OF THE INVENTION

The present invention generally relates to the field of wireless communication, and more particularly relates to a method and system for handling inter-domain handover of voice call from voice over long term evolution (VoLTE) to circuit switched (CS) domain in dual radio user equipment (UE).

BACKGROUND OF THE INVENTION

Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. The wireless networks can be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). Examples of multiple-access network formats include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.

These multiple access 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 an emerging telecommunication standard is Long Term Evolution (LTE). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology.

Currently a user equipment (UE) can establish a packet switched (PS) call with another UE over LTE network, wherein the LTE network provides voice over LTE service to the UE, and hence called as VoLTE network. When the UE is moving from VoLTE region to an area where Voice over LTE is not available or supported, and wishes to continue the call in the Circuit Switched (CS) domain from current PS domain, it has to follow the 3GPP TS 23.216 defined Single Radio Voice Call Continuity (SRVCC) procedures. In current scenario, SRVCC is implemented on the UE and on network side to provide voice call continuity from VoLTE to non-VoLTE area. This is primarily used in devices that support Single Radio or specifically does measurements using single antenna.

When handing over the VoLTE call to CS domain using existing SRVCC procedure, call delay is being observed in call continuity, due to, but not limited to, session transfer at the Network side from IP Multimedia Subsystem (IMS) domain to CS domain leading to time consumption, tuning of the UE to the CS domain, and possibility of handover failure, and the like.

Currently, UEs with dual radio capabilities are gaining popularity, wherein the UE, instead of single radio receiver with one or more antennas, comprises of dual radio receivers with one or more antennas on each radio receiver. The dual radio capable UE can use simultaneous global system for mobile communication (GSM) and LTE (SGLTE), wherein the UE can work simultaneously in the GSM and LTE modes. In most of cases LTE antenna is used for packet services and GSM for circuit switched services, but not limited to so.

In case of dual-radio support, like in SGLTE UE’s, there is no current method to provide faster handover or VoLTE call to CS domain to reduce the voice call interruption time, although the UE is already attached to CS domain using the second radio. Further, currently there is no method for the UE to assist the network to perform more reliable VoLTE to CS handover by using UEs own capabilities, and thereby reducing delay during hand over and improve the success rate of handover thus improve the quality of call continuity.

Some prior-arts have tried to address the data session or any other communication session suspension or continuity when UE moves to other communication radio technology by sending UE’s Tx/Rx capabilities to network. However the art does not disclose the method to assist network by means of providing UE capabilities. Also the art does not disclose the problem and solution to voice interruption time.

Thus, there exists a need for a system and method that can support two access technologies at the same time in dual-radio and dual link UE, and can reduce handover time by using UEs capability to remain registered in multiple technologies.

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

SUMMARY OF THE INVENTION

The various embodiments herein disclose a method and system for handling inter-domain handover of voice call from voice over long term evolution (VoLTE) to circuit switched (CS) domain in dual radio user equipment (UE).

According to an embodiment of the present invention, a method for handling inter-domain handover of voice call from VoLTE circuit switched Cell in dual radio user equipment (UE), the method comprises of sending, by the UE, an ATTACH request to a Mobile Management Entity (MME) with indication of simultaneous GSM and LTE (SGLTE) Dual radio capability, sending, by the UE, a cell identity (ID) of current registered CS RAT to an eNodeB when Voice call in LTE (VoLTE Call) needs to be continued over CS RAT(2G/3G), sending, by the eNodeB, a handover request comprising a target cell ID and a voice call continuity indication to the MME, validating, by the MME, whether the UE is SGLTE capable by verifying the voice call continuity indication, receiving, by a Mobile Switching Centre (MSC), the handover request transmitted from the MME if the UE is SGLTE capable, providing, by the MSC, the handover request from the MME to the target CS RAT, and switching, by the UE, from the VoLTE RAT to the CS RAT for continuing the voice call.

According to an embodiment of the present invention, the ATTACH request comprises of simultaneous Global System for Mobile communication (GSM and Long-term evolution (LTE (SGLTE) Dual radio capability information.

According to another embodiment of the present invention, the handover request comprises at least one of International mobile subscriber Identity (IMSI) of the UE, Identity information of the target CS RAT, Session Transfer Number (STN-SR), Correlation Mobile Station ISDN number (C-MSISDN), and SGLTE bit.

According to an embodiment of the present invention, the UE informs the SGLTE capability to the network by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request.

According to an embodiment of the present invention, the UE informs the network that UE supports Voice Call handover and is capable of assisting network for voice call handover by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request.

According to another embodiment of the present invention, a system for handling inter-domain handover of voice call from voice over long term evolution (VoLTE) to circuit switched (CS) domain, the system comprising a dual radio User Equipment (UE) adapted for sending an ATTACH/ TRACKING AREA UPDATE request along with a simultaneous GSM and LTE (SGLTE) Dual radio capability information to a Mobile Management Entity (MME), sending a cell identity (ID) of current registered CS RAT to an eNodeB when Voice call in LTE (VoLTE Call) needs to be continued over CS RAT(2G/3G), an eNode B adapted for sending a handover request comprising a target cell ID and a voice call continuity indication to the MME, a Mobile Switching Centre (MSC) adapted for receiving the handover request transmitted from the MME if the UE is SGLTE capable, and providing, by the MSC, the handover request from the MME to the target CS RAT.

According to another embodiment of the present invention, the UE can switch from the VoLTE RAT to the CS RAT for continuing the voice call, thereby reducing voice call interruption during inter-domain voice call handover.

The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understanding 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.

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 flow chart illustrating a method for handling inter-domain handover of voice call from VoLTE to circuit switched (CS) cell in dual radio user equipment (UE), according to an embodiment of the present invention.

Figure 2 is a schematic block diagram illustrating user equipment (UE) with simultaneous GSM and LTE (SGLTE) dual radio capability, 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.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and system for handling inter-domain handover of voice call from VoLTE to circuit switched (CS) cell in dual radio user equipment (UE), and thereby reducing voice call interruption duration during handover. 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 present invention describes a method and system for handling inter-domain handover of voice call from VoLTE to circuit switched (CS) cell in dual radio user equipment (UE), wherein the dual radio UE can be simultaneous GSM and LTE capable and the UE can work on GSM and LTE network simultaneously, while one radio accesses service from GSM, the other radio accesses service from the LTE. The present invention can be described with respect to the herein below mentioned embodiments, but not restrict the scope of the invention.

Figure 1 is a schematic flow chart 100 illustrating a method for handling inter-domain handover of voice call from VoLTE to circuit switched (CS) cell in dual radio user equipment (UE), according to an embodiment of the present invention,. According to the present invention, at step 102, the method comprises step of sending, by the UE, an ATTACH/TRACKING AREA UPDATE request along with a simultaneous GSM and LTE (SGLTE) Dual radio capability information to a Mobile Management Entity (MME). Initially, a voice call session can be active on one radio of the UE, wherein the radio can be handling the voice call over VoLTE cell. In an embodiment of the present invention, the voice call can be a mobile originated (MO) call. In another embodiment of the present invention, the voice call can be mobile terminated (MT) call. In another embodiment of the present invention, the voice call can be a conference call. The person having ordinarily skilled in the art can understand that the voice call can be of any type which is being handled by LTE cell accessed by one of the radios of the UE, without departing from the scope of the invention.

The UE can send the ATTACH/TRACKING AREA UPDATE request message to the MME. In an embodiment of the present invention, the UE can send the ATTACH/TRACKING AREA UPDATE request message upon identifying that, but not limited to, the UE is moving out of currently camped LTE cell and entering into coverage region of non-LTE cell where VoLTE call cannot be continued, the signal strength of LTE cell gets diminished, , and the like. The person having ordinarily skilled in the art can understand that the UE can handover due to any of the reasons from one cell to the other, as mentioned in the 3GPP standards, without departing from the scope of the invention.

In another embodiment of the present invention, the ATTACH request message comprises of simultaneous Global System for Mobile (GSM) and Long-term evolution (LTE) (SGLTE) Dual radio capability information that indicates the UE can access both GSM and the LTE over two radios.

In an embodiment of the present invention, the UE can inform the SGLTE capability to the currently camped network or MME by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request. In another embodiment of the present invention, the UE can inform the network that UE supports Voice Call handover by setting a SGLTE capability bit in MS Network capability Information Element (IE) in the ATTACH request.

Further, at step 104, the method comprises of sending, by the UE, a cell identity (ID) of current registered circuit switch (CS) radio access technology (RAT) to an eNodeB when Voice call in LTE (VoLTE Call) needs to be continued over CS RAT (2G/3G). The UE can fetch the cell identity (ID) of the CS RAT to which the second radio of the UE is currently registered to which the UE would like to switch to continue the voice call. The fetched CS RAT cell ID can be transmitted to the eNodeB on which the UE is currently camped and having active LTE voice call so that the UE can camp on the currently registered CS RAT and continue the voice call.

At step 106, the method comprises of sending, by the eNodeB, a handover request comprising a target cell ID and a voice call continuity indication to the MME. The eNodeB receives the CS RAT cell ID from the UE and identifies the received cell ID as target cell ID. The target cell ID can be transmitted to the MME along with the voice call continuity indication as part of the handover request message. The voice call continuity indication bit can indicate the willingness of the UE to handle or continue the voice call on CS RAT. In an embodiment of the present invention, along with the target cell ID and voice call continuity indication, the handover request message transmitted by the eNodeB to the MME can comprise at least one of, but not limited to, International mobile subscriber Identity (IMSI) of the UE, Identity information of the target CS RAT, Session Transfer Number (STN-SR), Correlation Mobile Station ISDN number (C-MSISDN), SGLTE bit and the like.

In another embodiment of the present invention, SRVCC bit can be used in the ATTACH request message to indicate voice call handover to the CS RAT from the current LTE RAT.

Further, at step 108, the method comprises the MME receiving the handover request from the eNodeB. Upon receiving the handover request comprising target cell ID and voice call continuity indication from the eNodeB, the MME can validate the SGLTE capability of the UE, wherein the SGLTE capability of the UE can be validated by verifying the call continuity indication bit mentioned in the handover request. The person having ordinarily skilled in the art can understand that various methodologies can be used for verifying the call continuity information bit while validating the SGLTE capability of the UE, without departing from the scope of the invention.

Further, at step 110, the method comprises the step of receiving, by a Mobile Switching Centre (MSC), the handover request transmitted from the MME if the UE is SGLTE capable. Upon verifying that the voice call continuity information bit and thus validating the UE being SGLTE capable, the MME can transmit the handover request received from the eNodeB to the mobile switching centre (MSC). The MSC can receive the handover request from the MME, wherein the MME can identify that the voice call, which is currently handled by the LTE RAT, can now be handled by the CS RAT registered with the MSC.

Further, at step 112, the method comprises step of providing, by the MSC, the handover request from the MME to the target CS RAT. Once the MSC receives the handover request from the MME, the MSC identifies the target CS RAT based on the cell ID present in the handover request, and transmits the handover request to the target CS RAT. The target CS RAT receives the handover request and identifies that it has to maintain continuity of the voice call of the UE.

Further, at step 114, the method comprises step of switching, by the UE, from the VoLTE RAT to the CS RAT for continuing the voice call, thereby reducing voice call interruption during inter-domain voice call handover. Upon sending the handover request to the MME, the UE can automatically switches to the registered CS RAT and continues the voice call on the CS RAT from the VoLTE RAT by sending voice packets on the CS RAT. In another embodiment of the present invention, the UE waits till it receives an acknowledgement from the MME that the handover request has been transmitted to the MSC and upon receiving the acknowledgement, the UE switches to the CS RAT for continuing voice call. As the voice call is switched from VoLTE domain to CS domain without any delay in time for selecting the CS cell to camp on and time for registering with the new CS cell, the present invention can provide a suitable solution that can reduce voice call interruption problem during inter-domain handover.

Consider an exemplary scenario illustrating the method for handling inter-domain handover of voice call from VoLTE to circuit switched (CS) Cell in dual radio user equipment (UE), according to an embodiment of the present invention. According to the scenario, a mobile phone with dual radios, radio1 and radio2, can be having SGLTE capability. The radio1 is camped on the LTE RAT and supports VoLTE while the radio2 is camped on the CS domain, wherein the RAT can be at least one of 2G or 3G. The mobile phone can be having an ongoing voice call (VoLTE) over the radio1 that is camped on the LTE RAT. Thus, the ongoing voice call can be a packet switched (PS) voice call.

While the radio1 of the mobile phone has registered itself with the LTE RAT, the radio2 of the mobile phone can register itself with the 2G/3G RAT. In an embodiment of the present invention, the mobile phone can camp on the CS RAT, but continue being in the idle mode as the mobile phone is continuing with the ongoing voice call over the LTE RAT.

After certain time period, the mobile phone identifies that it is moving out of the coverage region of the LTE where VoLTE call is supported. Thus, the mobile phone identify that the connection might get lost, thereby decrease in the quality of voice call and further eventual discontinuity of the voice call. Therefore, according to the present invention, in measurement reports, the mobile phone can provide the cell ID of the CS RAT on which the radio2 of the mobile phone is camped on.

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Based on the measurement reports, the eNodeB can send Handover Required command to MME. The MME receives the handover request and identifies the SGLTE dual radio capability information. Upon identifying the SGLTE dual radio capability information, the MME validates the SGLTE dual radio capability of the mobile phone by verifying the voice call continuity information set by the mobile phone.

Upon identifying that the mobile phone is dual radio capable based on the SGLTE dual radio capability information and voice call continuity information, the MME can identify the MSC and can transmit the handover request to the MSC on which the target CS RAT is registered. The MSC identifies the target RAN for call handover. Upon receiving the handover request, CS RAT has to handle the voice call of the mobile phone to provide continuity to the voice call.

The mobile phone switches to the CS domain from the VoLTE RAT and initiates transmitting the voice packets of the voice call on the CS RAT. As the switching from VoLTE to the CS domain can happen dynamically, the mobile phone will not perform lower layer tuning but switches instantaneously to the CS domain from the VoLTE domain, and thereby maintaining the continuity of the voice call without interruption time. According to the present scenario, the voice call is also switched from PS voice call to CS voice call.

Figure 2 is a schematic block diagram illustrating user equipment (UE) 200 with simultaneous GSM and LTE (SGLTE) dual radio capability, according to an embodiment of the present invention. The block diagram illustrates the UE 200 interacting with two different radio access technologies (RATs), LTE RAT and circuit switched (CS) RAT (either 2G RAT or 3G RAT). The block diagram comprises of a modem 202, two radios, radio1 204a and radio2 204b, wherein the radio1 204a comprises of two antennas LTE primary antenna 206a, and LTE secondary antenna 206b, the radio2 204b comprises of an antenna GSM/WCDMA/TDSCDMA antenna 206c, a LTE RAT 208 that can provide LTE network coverage to the radio1 204a, and a 2G/ 3G RAT 210 that can provide GSM/ WCDMA/ TDSCDMA type of 2G/ 3G network coverage to the radio2 204b.

According to the present invention, the dual radios radio1 204a and the radio2 204b can comprise of one or more antennas to access network. The radio1 204a accesses the LTE RAT 208 to exchange packet switched (PS) data packets over at least one of the LTE primary antenna 206a and the LTE secondary antenna 206b. In an embodiment of the present invention, the radio1 204a can use the LTE primary antenna 206a for accessing the LTE network while the LTE secondary antenna 206b is on idle state. In another embodiment of the present invention, the LTE primary antenna 206a can be in idle state while the LTE secondary antenna 206b is accessing the LTE network. In another embodiment of the present invention, both the LTE primary antenna 206a and the LTE secondary antenna 206b can be accessing the LTE network. In another embodiment of the present invention, both the antennas of the radio1 204a can be used only when the quality of the LTE network is going low. The person having ordinarily skilled in the art can understand that any type of combination of the antennas of the radio can be used to access the network to provide better quality of service to the user without departing from the scope of the invention.

Further, the radio2 204b of the UE 200 can access the 2G/3G RAT 210 to exchange circuit switched (CS) data over the GSM/WCDMA/ TDSCDMA antenna 206c. It is to be observed that both the antennas can register themselves with the respective network independently. The modem 202 can be connected with both the antennas and thus the modem 202 can establish connection with other UEs over either LTE RAT 208 or the 2G/3G RAT 210. PS data can be transmitted between the modem 202 and the LTE RAT 208 while CS data can be transmitted between the modem 202 and the 2G/3G RAT 210. The connection established between the modem 202 and the LTE RAT 208 and the connection established between the modem 202 and the 2G/3GRAT 210 is represented with the dotted line in the block diagram.

The present embodiments have been described with reference to specific example embodiments; it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.