WO2012053884A1

WO2012053884A1 - Location independent approach to session transfer for real-time voip session

Info

Publication number: WO2012053884A1
Application number: PCT/MY2010/000296
Authority: WO
Inventors: Khong Neng Choong; Cheng Suan Lee
Original assignee: Mimos Berhad
Priority date: 2010-10-22
Filing date: 2010-11-25
Publication date: 2012-04-26
Also published as: MY171032A

Abstract

A plurality of user devices (UD1...UDn, TD1...TDn) adapted to communicate in Session Initiation Protocol communicatively coupled with a session transfer application server (301 ) hosted on an IMS subsystem (201 ). Upon receiving a session transfer request from an end user device (UD1 ), the server (301 ) alerts or rings all registered target devices (TD1.TDn) by the same user, and leaves the user himself or herself to select which device he/she prefers to take the session forward at the point of time. Once the selection has been made, the system, by a series of SIP messages cancels the alerting or ringing session on the remaining devices and transfers the session between the first user (U1 ) and second user (U2) to a target device (TD1 ) of the first user.

Description

LOCATION INDEPENDENT APPROACH TO SESSION TRANSFER FOR REAL-TIME VOIP SESSION

FIELD OF THE INVENTION

This disclosure relates generally to telecommunications and more particularly, to methods and systems for real time session transfer in Voice over Internet Protocol (VoIP) services.

BACKGROUND OF THE INVENTION

The object of ubiquitous computing is that users can access any service (such as voice, video or data) through any operation network, anywhere at any time with any device. Hence, it is expected that users would change their communication devices according to the surrounding environment during a communication session, as to suit his/her preference at any point in time. For example, a desktop PC is used for faster processing where mobility is not the requirement; while a mobile phone is used to watch a video clip while on the move. There are also times where a user started a session on the desktop but decided to switch it over to the mobile phone when there is a need to be on the move without terminating the session. This is called as session transfer or device switching where users switch their session from the original (current) device to target (next) device.

Session transfer from one communication device to another target device is generally known in the art. Session transfer in Voice over Internet Protocol (VoIP) services based on Internet Protocol (IP) Multimedia Subsystems (IMS) is also known in the art.

The Internet Protocol (IP) Multimedia Subsystem (IMS) is a standard that has been developed to define the control and integration of multimedia services in a core, packet- switched network. In particular, the IMS architecture defines a set of logical functions that use a signaling protocol known as the Session Initiation Protocol (SIP) to establish communication sessions in an IP network. A "session" may be, for example, a one-to-one voice call or a more complex interaction, such as a one-to-many conference call involving multimedia services. SIP may also be used to facilitate voice over IP (VoIP) services, in which voice is transported in IP data packets that are re-assembled and converted into an audio signal for the recipient. IMS may be characterized as a standardized way to connect IP devices and networks using SIP. US20060092970 discloses a system and method for VoIP call transfer using Instant message service in an IP Multimedia Subsystem. The Instant Messaging capability of an IP multimedia subsystem is utilized to support call transfer service for VoIP users. A call transfer request from a first VoIP user to a second VoIP user is sent to the IP multimedia subsystem in a predetermined non-standard SIP communication. The IP multimedia subsystem invokes Instant Messaging service in response to the predetermined nonstandard SIP communication, and Instant Messaging service is then utilized to support the call transfer dialogue.

US 7171221 discloses a system and method of automatically transferring a call between telephones based on the distance between the two telephones is provided. First, the proximity of a first telephone to a second telephone is determined. If the proximity is within a predetermined limit or threshold, calls directed to the first telephone are transferred to the second telephone. Security of the transfer may be ensured to prevent fraudulent use of the subscription of either telephone. Procedures are provided which permit any the above-mentioned steps to be performed either at the level of the individual telephones involved in the transfer, or by an element of the network, such as an MSC or HLR. US 6130938 teaches a method of forwarding calls, the method comprises storing a list of possible forwarding destinations for each subscriber, maintaining a behavior database for each subscriber indicating the probable location of the subscriber at any particular time, and forwarding incoming calls to the probable location determined from the behavior database. The behavior database is dynamically updated according to the success rate of the forwarded calls.

US 6038451 discloses a location based method of and system for processing a telephone call to a wireless telephone number associated with a mobile telephone unit forwards the call to a registered wire line number if the mobile unit is located near the geographic location associated with the wire line number. In response to a call placed to a wireless telephone number, the system determines the geographic location of the mobile unit associated with the wireless telephone number. If the mobile unit is near a registered location, the system forwards the call to the registered wire line number associated with the registered location. In another known method, a location server may be made use of to intelligently and automatically select the target device based on the location and proximity of the current device with the target device. However, this approach relies on very accurate location estimation and tracking algorithm (i.e. less than 1 m accuracy), which is a challenge with today's wireless technology. The existing wireless location system has some limitations as follows: the GPS is unable to function with indoor devices, while indoor location tracking with Wi-Fi is lacked of accuracy; also short-range technology like Bluetooth has some challenges in terms of speed on device discovery and connection establishment.

But all the systems and methods known in the art can be employed only in two devices directly in contact with each other. Moreover, the prior art methods require the user to know, remember and enter the contact or IP address of the target device during the session. Such restriction limits and degrades user experience because it is not seamless where the ongoing application session is interrupted. Therefore, the main object of this invention is to eliminate the error-prone steps of session transfer carried out by both the users, who have to remember and enter the contact of target device, and also by the location server, which must accurately estimate and track the location of all devices.

It is yet another object of the invention to disclose a system and method to transfer ongoing VoIP call from one active device to an inactive target device physically selected by the user, from a plurality of target devices during the call.

SUMMARY OF THE INVENTION

The present invention simplifies the process of session transfer by removing the need of location server to enable device switching. This is done by shifting the responsibility of session transfer to the central IMS subsystem to keep track of all registered sessions/status and devices whereby whenever there is a session transfer request, all the accessible devices (authorized to particular users) will be contacted and alerted (for example, with a ringing sound) and allowing users themselves to decide the target device by simply answering the ringing device. The main advantage of this approach is that no expensive location server is needed and yet users are given real-time selection of devices based on their current physical locations.

It is disclosed herein, a system to transfer a current communication session between a first user (U1) and a second user (U2) to a target device (TD1) of the first user (U1) comprising:

a) a plurality of user devices (UD1...UDn) and target devices (TD1...TDn) adapted to communicate according to the Session Initiation Protocol; b) an IMS subsystem communicatively coupled with the said devices (UD1 ...UDn, TD1...TDn); and c) a session transfer application server (ST AS) (301 ) hosted on the IMS subsystem (201 ) capable of: sending a SIP INVITE message to a plurality of target user devices (TD1 ...TDn) in response to a request for session transfer from the first user device (U1 ); sending out SIP CANCEL message to all other target devices (TD2...TDn) on receipt of a SIP OK Message from at least one target user device (TD1 ); sending out a SIP REFER message received from the ST AS (301 ) to the second user device (UD2) resulting the second user device (UD2) to return a SIP INVITE message; sending a SIP OK message and SIP ACK message with the finalized session description payload to the second user device (UD2) and target user device (TD1 ) respectively, thereby transferring the session between the first user (U1 ) and second user (U2) to the target user device (TD1 )and sending a SIP BYE message to the first user device (UD1 ) thereby ending the communication session between the first user device (UD1 ) and second user (U2).

In another aspect of the invention, disclosed herein is method of transferring a current communication session between a first user device (UD1 ) of first user (U1 ) and a second user (U2) to a target user device of the first user (TD1 ) selected from a plurality of target devices (TD1 ...TDn), wherein the said devices (UD1...UDn, TD1 ...TDn) are communicatively coupled with an IMS subsystem (201 ), said method comprising any of the steps of:

a) sending SIP INVITE messages (712,714) from a session transfer application server (301 ) hosted on the IMS subsystem (201 ) to a plurality of accessible devices (TD1 ...TDn) on receipt of session transfer request (702) as a SIP message from the first user (U1); b) sending out SIP CANCEL message (724) from the server (301 ), thereby canceling the remaining SIP INVITE message (714) sent to other target devices (TD2...TDn) on receipt of a SIP OK message (718) from at least one target device (TD1 ); c) sending a SIP REFER message (726,728) from the server (301 ) together with at least identification, routing, and session description information (718) provided by the first target device (TD1 ), to the second user device (UD2); d) second user device (UD2) sending an SIP INVITE message (730) with the identification information of the first target device (TD1 ) and suggested session description payload back to the server (301 ); e) the said server (301 ) sending a SIP OK message (732) and ACK message with finalized session description payload (738) to the second user device (UD2) and the first target device (TD1 ) respectively; and f) the said IMS subsystem sending a SIP BYE message (740,742) to the first user device (UD1 ) and ending the session between first user device (UD1 ) and second user (U2).

Also disclosed herein, in yet another aspect of the invention, a computer readable media containing executable programming instructions that cause the computer to transfer a current communication session between a first user device (UD1 ) of first user (U1 ) and a second user (U2) to a target user device of the first user (TD1 ) selected from a plurality of target devices (TD1 ...TDn) communicatively coupled with an IMS subsystem (201 ). BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the end user and server architecture of one embodiment of the invention Figure 2 shows the internal architecture of an IMS-enabled device in accordance with one embodiment of the invention

Figure 3 shows the internal architecture of a Session Transfer Application Server (STAS) in accordance with one of embodiment of the invention

Figure 4 illustrates the process flowchart of one embodiment of the invention

Figure 5 illustrates session registration process in an exemplary case using an embodiment of the invention

Figure 6 illustrates call establishment process in an exemplary case using an embodiment of the invention

Figure 7 illustrates an exemplary situation of call transfer in one of the preferred embodiments of the invention

DETAILED DESCRIPTION OF THE INVENTION

The invention and its various embodiments is better understood by reading the description along with the accompanying drawings which appear herein for purpose of illustration only and does not limit the invention in any way.

The 3GPP describes an Internet Protocol (IP) multimedia subsystem (IMS). The present invention expands the capabilities of the IMS by providing session transfer service for end users. The system as described uses the Instant Messaging capability within IMS in one or more ways. A person skilled in the art will understand the architecture and workings of the IMS. IMS consists of at least three basic layers: an application layer to hold application and content servers which execute value added services for the end user; the control layer to host network control servers, which manage call and session setup, modification and release; and a connectivity or transport layer consisting of routers, switches and other user plane functions. The routers and switches provide transport capabilities for both control plane and user plane traffic.

In the IMS specification the "core" of IMS comprises two main nodes: the Call Session Control Function (CSCF) and the Home Subscriber Server (HSS). The Call Session Control function (CSCF) is the heart of the IMS architecture and is used to process Session Initiation Protocol (SIP) signaling. The main function of the CSCF is to provide session control for end users and applications using the IMS network. Session control includes the secure routing of the SIP messages, subsequent monitoring of the SIP sessions and communicating with the policy architecture to support media authorization.

Referring to FIG 1 , in one embodiment of the invention, a plurality of IMS-enabled end user devices (UD1...UDn) in a session is shown. In an exemplary case, a user has 3 devices (UD1...UDn, TDL. Dn) including a current active device (UD1), which has an active session with a second user's device (UD2) via the central IMS Core Components (210) that in turn rely on the Session Transfer Application Server (STAS) (301) to perform session transfer. Then, upon receiving a session transfer request from an end user device, the server alerts or ring all registered devices by the same user, and leaving the user himself or herself to select which device he/she prefers to take the session forward at the point of time. Once the selection has been made, the system then cancels the alerting or ringing session on the remaining devices. In cases where more than one target device has answered, the system recognizes only the first target device that successfully sent the call pick-up message to the server.

In yet another embodiment, the server (301 ) may be first requested to log down all active and inactive sessions of all end user devices.

From the performance aspect, the proposed invention confines the transmission of SIP Invite and SIP Refer message to within the local IMS subsystem. This means these messages are not sent from one end user device to another corresponding device in an end-to-end manner. Hence, the performance will be better as the latency is reduced.

User has a choice to select a target device on-the-fly so as to complete the transfer. User just needs to pick up the ringing device (TD1 ) (i.e. the target device referred by the Application Server) to complete the transfer.

The transfer is performed by the Session Transfer Application Server (STAS) (301 ) hosted on the IMS subsystem (201 ) (i.e. S-CSCF), which sends standard SIP Invite message to a plurality target devices. The transfer is performed by the server, which pages the target device before communicating to the Corresponding Node (CN), which is the second user (UD2).

Figure 1 shows the end user and system architecture of one embodiment of the invention. It consists of a plurality of IMS-enabled end user devices (UD1 ...UDn, TD1 ...TDn). In an exemplary case, a user has 3 devices (UD1 , TD1 , and TD2) including a current active device (UD1 ), which has an active session with a second user's device (UD2) via the central IMS Core Components (201 ) that in turn rely on the Session Transfer Application Server (STAS) (301 ) to perform session transfer. Upon receiving the session transfer request from first device, STAS will carry out a series of message exchanges (denoted as dotted lines) so as to help transfer the currently active session from one device into another. In this case, the session is transferred from UD1 to TD1. Figure 2 shows the internal architecture of an IMS-enabled device in accordance with the provisions of the invention. The session transfer intelligence sits at the application level and consists of two modules. The first module is known as the Session Management Module (210), which is responsible for registering and de-registering the application with the central IMS core. It is also designed to work with the STAS (301 ) as to perform session transfer. The second module is called Action Handler (212), which is an application hooks for application to invoke underlying IMS services such as registration and session transfer. It interfaces with the user application through key pressing or mouse button clicking.

Figure 3 shows the internal architecture of the Session Transfer Application Server (STAS) (301 ). It sits on top of the standard IMS Core (201 ) as an application server. The protocol interface between the IMS core and SIP application server is standard IMS SIP protocol.

The STAS (301) is made up of 4 components: Session Manager (302), Session Database (303), Session Transfer Manager (304) and Session Router (305). The first component is the Session Manager (302) that is responsible for tracking all sessions in the system including details about, when the session is first created, transferred and eventually terminated. All the tracked session are logged into the Session Database (303). The Session Database (303) is designed to record all past and current sessions including the status information arranged by date and time, grouped by specific SIP URI or registered name. The third component is Session Transfer Manager (304); it is responsible for managing session transfer. This involves sending various SIP messages to various SIP entities in the network such as the various devices registered under the current SIP URI, corresponding nodes as well as the requesting active device. Fourth component is Session Router (305) which communicates with the IMS core components (201).

Figure 4 shows the flowchart of one of the embodiment of the invention. The flowchart is shown in a waterfall-structured manner so as to illustrate the various different entities involved during the session transfer session.

The interaction starts off with user requesting the server for transferring the current VoIP session (404). This is done by either pressing certain key on the keypad or keyboard of the user device (UD1 , represented as Alice) or clicking on some button on the screen, or even through voice command. The session transfer request is then sent to the server (301) (which refers to the combination of the standard IMS core and STAS). Upon receiving the request, the server (301 ) first checks on all accessible devices by this requestor by consulting the session database. The server later proceeds by sending SIP Invite message(s) to all accessible devices (408). It then waits until the first SIP OK plus the Session Description Protocol (SDP) message is returned from one of the many accessible devices (412). This is referred as Target Device (TD1 ), or as in the exemplary case, Alice 2. The server then sends SIP Cancel message to the remaining accessible devices as to cancel the earlier SIP Invite message (414). The next step is for the server (301) to send a SIP Refer message to the Corresponding Node (CN), i.e., UD2, passing over the SIP URI of the TD1 (416).

The CN (UD2) on receiving the SIP Refer message then sends (418) a SIP Invite plus its own SDP message back to the server (301). Now the server (301) selects a common media (choice of codec, medium etc.) for use by both TD1 and UD2 to establish a new session as the continuity of the existing session. Once this is selected, the server (301) sends a SIP OK plus the finalized SDP to UD2 (420). Next, the server (301) sends a SIP ACK with the finalized SDP to TD1 (422). With receipt of this message, both ends (UD2 and TD1 ) then establish a new session based on the configuration and settings found in the finalized SDP. In the last step the server (301 ) may also send a SIP Bye message back to the requesting device (424). This is to cancel the old session that is taking place between the requesting device (UD1 ) and UD2.

Figure 5 shows the IMS registration process with extra message exchange to enable the session transfer mechanism. In this illustration, Alice (U1 ), who is the requesting user sends SIP Info message that carries customized field - event: register, to the IMS core. IMS core could route this customized message to the specific STAS (301 ). The STAS (301 ) will then send a SIP Subscribe to the IMS Core so as to monitor the status of the registered end user.

FIG 5, 6 and 7 illustrates examples using the systems and processes of one of the embodiments of the invention. There are two users Alice (U1 ) and Bob (U2) with IMS enabled devices (UD1 ...UDn, TD1...TDn). Figure 6 shows the message flow where Alice (U1 ) makes a call. The SIP invite is sent (602) from Alice (UD1) device to the IMS core (for originating call) (201 ). This SIP invite is then forwarded to the STAS (301 ) as specified or configured in the IMS Initial Filter Criteria (IFC) (604). At the STAS (301 ), information about this SIP invite message is extracted and stored into the local database (i.e. the session database). Then, the message is further forwarded (606) to the terminating IMS Core (201 ). Based on the IFC settings, the message is again gets forwarded (608) to the same STAS for recording. Eventually, the SIP invite message reaches (612) Bob (UD2), where Bob (UD2) would accept by sending a SIP OK (614) back to Alice (UD1 ) passing (614-620) through the intermediate IMS core (201 ) and STAS (301 ) as illustrated.

Figure 7 shows the detailed message exchange for transferring call, in this case, from Device named Alice (UD1 ) to Alice2 (TD1 ). This session starts when user Alice triggers the session transfer request to the STAS (301) in the form of SIP Info message (702), which carries the customized event field of Transfer. This SIP Info is first received by the IMS core and later forwarded (704) to STAS (301) for processing. First, multiple SIP Invite messages (708,710) are sent to all accessible devices (TD1...TDn). Assuming user Alice (U1) picks up the call using Device Alice2 (TD1), a subsequent SIP Cancel message is then sent (724) to the remaining devices(TD2...TDn) to cancel the earlier SIP Invite messages. STAS (301) then sends a SIP Refer (728) to Bob (UD2) through the IMS core (201 ), resulting Bob (UD2) to send a SIP Invite (730) back to STAS (301). The new call is eventually established after STAS (301 ) has sent the SIP OK message (732) to Bob (U2) and the SIP Acknowledge message (738) to Device Alice (TD1 ).

ADVANTAGES

Present invention simplifies the process of session transfer by removing the needs of location server to enable device switching. This can be done by shifting the responsibility to the central IMS server to keep track of all registered sessions/status and devices whereby whenever there is a session transfer request, all the accessible devices (authorized to particular users) will be contacted and alerted (like a ringing sound) and allowing users themselves to decide the target device by simply answering the ringing device. The main advantage of this approach is that no expensive location server is needed and yet users are given real-time selection of devices based on their current physical locations.

User has a choice to select a target device on-the-fly as to complete the transfer. User just needs to pick up the ringing device (i.e. the target device referred by the Application Server) to complete the transfer. In another embodiment, user could also be provided with a list of target devices to choose from, by the IMS server while performing session transfer. The list of target devices could be presented in a graphical or text-based user interface on the user devices. It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not restricted to the above examples but may vary within the scope of the claims. Further, the above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

A system to transfer a current communication session between a first user (U1 ) and a second user (U2) to a target device (TD1 ) of the first user (U1 ) comprising: a) a plurality of user devices (UD1 ...UDn) and target devices (TD1 ...TDn) adapted to communicate according to the Session Initiation Protocol; b) an IMS subsystem communicatively coupled with the said devices (UD1 ...UDn, TD1 ...TDn); and c) a session transfer application server (ST AS) (301 ) hosted on the IMS subsystem (201 ) capable of: sending a SIP INVITE message to a plurality of target user devices (TD1...TDn) in response to a request for session transfer from the first user device(U1 ); sending out SIP CANCEL message to all other target devices (TD2...TDn) on receipt of a SIP OK Message from at least one target user device (TD1 ); sending out a SIP REFER message received from the STAS (301 ) to the second user device (UD2) resulting the second user device (UD2) to return a SIP INVITE message; sending a SIP OK message and SIP ACK message with the finalized session description payload to the second user device (UD2) and target user device (TD1 ) respectively, thereby transferring the session between the first user (U1 ) and second user (U2) to the target user device (TD1 ) and sending a SIP BYE message to the first user device (UD1 ) thereby ending the communication session between the first user device (UD1 ) and second user (U2). A system as claimed in claim 1 wherein the said user devices (UD1...UDn, TD1 ...TDn) are communication devices.

A system as claimed in claims 1 or 2 wherein the said communication devices (UD1 ...UDn, TD1 ...TDn) are capable of initiating a session transfer request, storing the session description in a database (303) and responding to session transfer requests.

A method of transferring a current communication session between a first user device (UD1 ) of first user (U1 ) and a second user (U2) to a target user device of the first user (TD1 ) selected from a plurality of target devices (TD1 ...TDn), wherein the said devices (UD1 ...UDn, TD1 ...TDn) are communicatively coupled with an IMS subsystem (201 ), said method comprising any of the steps of: a) sending SIP INVITE messages (712,714) from a session transfer application server (301 ) hosted on the IMS subsystem (201 ) to a plurality of accessible devices (TD1 ...TDn) on receipt of session transfer request (702) as a SIP message from the first user (U1); b) sending out SIP CANCEL message (724) from the server (301 ), thereby canceling the remaining SIP INVITE message (714) sent to other target devices (TD2...TDn) on receipt of a SIP OK message (718) from at least one target device (TD1 ); c) sending a SIP REFER message (726,728) from the server (301 ) together with at least identification, routing, and session description information (718) provided by the first target device (TD1 ), to the second user device (UD2); d) second user device (UD2) sending an SIP INVITE message (730) with the identification information of the first target device (TD1) and suggested session description payload back to the server (301);

e) the said server (301) sending a SIP OK message (732) and ACK message with finalized session description payload (738) to the second user device (UD2) and the first target device (TD1) respectively; and the said IMS subsystem sending a SIP BYE message (740,742) to the first user device (UD1) and ending the session between first user device (UD1) and second user (U2).

5. A computer readable media containing executable programming instructions that cause the computer to operate in accordance with the method of claim 4.