UMTS call handling methods and apparatus

Abstract

Methods and apparatus for transparently switching a local instance of a UMTS protocol-based call from a first card or module of a media gateway to a second card or module of the media gateway, such that the remote end of the call is not aware that the call has been switched between the first and second cards or modules. Moreover, initially establishing call media flow may include implementing two timers of different duration during which call-initialization is retried if no Positive-Acknowledgement of call initialization is received, where a shorter-duration timer is relied upon to attempt retries if a Negative-Acknowledgement is received, and a longer-duration timer is relied upon to attempt retries if neither a Positive-Acknowledgement nor a Negative-Acknowledgement is received.

Description

BACKGROUND

Switchover is an important feature of media gateways to support scheduled in-service upgrade and to handle unexpected card failures. When a working service module or card of a media gateway fails, the media gateway must include provisions to move or “switchover” active channels onto a backup module or card. Moreover, it is desirable that the switchover be transparent to the remote end of any active calls, but this can be hard to achieve in some cases, such as in IuUP-based calls used in UMTS networks.

That is, at least according to the standard IuUP protocol state machine, a UMTS IuUP call instance cannot be transparently switched from one service card over to another service card because, to transit from the Null state to the Transfer Data Ready state, an IuUP call instance must go through the Initialization state, and must send out a new IuUP INIT message to the remote peer and receive a positive acknowledgement.

There is also a need in this area of technology for significantly reducing call drop rates and increasing service provider revenue. For example, when a packet (IP or ATM) network has high packet loss, the IuUP/NbUP INIT messages to initiate a UMTS call are often lost, and cannot reach the far-end peer. One or more retries may be attempted but, eventually, after a configured timer expires without receiving any positive acknowledgement message, the local end stops sending the INIT messages, and the call is dropped. In another scenario, when the local end starts to send INIT messages but the far-end has not yet been set up, the INIT messages sent by the local end will be dropped by the far end. Again, one or more retries may be attempted but, eventually, after a configured timer expires without receiving any positive acknowledgement message, the local end stops sending the INIT messages, and the call is dropped.

The standard UMTS IuUP protocol fails to handle these scenarios properly because it does not differentiate between the “NEGATIVE Acknowledgement” case, which means a definitive negative response, and the “No Acknowledgement” case, which means lack of any positive or negative response and may need additional time for retries. A single timer is used for both cases, which is usually small in order to speed up the decision at the “NEGATIVE Acknowledgement” case, but not sufficiently long to accommodate the “No Acknowledge” case.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic view of at least a portion of an embodiment of apparatus and/or network architecture according to aspects of the present disclosure.

FIG. 2 is a schematic view of at least a portion of an embodiment of the apparatus and/or network architecture shown in FIG. 1.

FIG. 3 is a schematic view of at least a portion of an embodiment of an IuUP protocol based state machine according to aspects of the present disclosure.

FIG. 4 is a flowchart diagram of at least a portion of an embodiment of a method according to aspects of the present disclosure.

FIG. 5 is a flowchart diagram of at least a portion of an embodiment of a method according to aspects of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Referring to FIG. 1, illustrated is a schematic view of at least a portion of one embodiment of a media gateway 100 (or similar switching apparatus) according to aspects of the present disclosure. The media gateway 100 includes at least two service cards 120, 125, each of which are configured to handle at least one local IuUP call instance 130. The local call instance 130 is initially handled by service card 120 and is then switched over to service card 125 (as indicated by the dashed lines). However, such switchover between service cards 120, 125 is transparent to the associated, remote IuUP call instance 140, which communicates with the local call instance 130 via IuUP protocol over an ATM, IP or other network 105.

Referring to FIG. 2, illustrated is a schematic view of at least a portion of one embodiment of the media gateway 100 shown in FIG. 1, herein designated by the reference numeral 200. The media gateway 200 includes wireless service modules 210, 215, each of which may be substantially similar to and/or include the service cards 120, 125 shown in FIG. 1. Each wireless service module 210, 215 includes a corresponding switchover handling module 220, 225, respectively, which are configured to cooperate to transparently switchover a call with a remote terminal 240 (e.g., a RAN)—that is, switchover the call in a manner that is transparent to the remote terminal 240.

An active one of the wireless service modules 210, 215 (e.g., module 210 in the embodiment and status illustrated in FIG. 2) is configured to receive switchover instruction from a control module, which may be located elsewhere within the media gateway 200. The switchover handling module 220 is configured to generate a Local-Init-Only message 230, possibly in addition to performing other tasks in response to the switchover instruction. The active wireless service module 210 and/or its switchover handling module 220 then sends the Local-Init-Only message 230 to a “peer” of the active wireless service module (e.g., module 215 in FIG. 2).

The peer switchover handling module 225 is configured to receive the Local-Only-Init message 230. The switchover handling module 225 (as well as module 220) is also configured to adjust its state machine, enter an active state, and suppress sending of the UMTS INIT message to the remote terminal 240, as may otherwise be required by the UMTS Iu-UP protocol, possibly in addition to performing other functions of taking over as the new active wireless service module. Normal protocol messaging required for the active state by the UMTS Iu-UP protocol may then be sent to the remote terminal 240.

According to aspects of the present disclosure, at least in some embodiments and implementations, the newly active wireless service module will not have to go through a negotiation process with the remote radio access network or terminal 240. In some instances, this can decrease the risk of dropping the call in progress.

Aspects of the present disclosure are also demonstrated in FIG. 3, which is a schematic view of a modified portion of the standard IuUP protocol state machine (such as is represented by FIG. B.2 in the 3GPP specification of 3GPP TS 25.415). Only the portion used by IuUP Support Mode is shown in FIG. 3. However, at least the illustrated portion of the modified IuUP protocol state machine is herein designated by the reference numeral 300.

An IuUP Support Mode call instance can be in one of the following states: Null state 301, Initialization state 302, and SMpSDU Data Transfer Ready state 303. To transition from the Null state 301 to the Transfer Data Ready state 303 in the standard IuUP protocol state machine, an IuUP call instance must go through the Initialization state 302, and must send out a new IuUP INIT message to the remote peer and receive a positive acknowledgement. However, at least in one embodiment according to aspects of the present disclosure, such as shown in FIG. 3, a direct transition 305 between the Null state 301 and the Data Ready state 303 is added, thus allowing transition without sending out any IuUP INIT message to the remote peer and without waiting for any acknowledgement from the remote peer.

Aspects of this transparent IuUP switchover can minimize the service impact to the network when, for example, a media gateway needs to perform a scheduled in-service upgrade or handle an unexpected card failure, and needs to move IuUP calls from the active card to the backup card. Of course, other advantages are also within the scope of the present disclosure.

Referring to FIG. 4, illustrated is a flow-chart diagram of at least a portion of one embodiment of a method 400 according to aspects of the present disclosure. The method 400 includes at least two possible initialization steps 410a, 410b. In step 410a, each channel is initialized to wait for a remote INIT message. In step 410b, local initialization is performed, and an INIT message is sent to the remote terminal. Either of steps 410a and 410b may be performed. In one embodiment, if step 410b is performed, one or more digital signal processor (DSP) and/or other processing means within or otherwise associated with the media gateway may still report received INIT messages to the host application.

A decisional step 420 determines when a module or card fails, at which time the host application may initialize the backup card in a step 430 and locally initialize one or more channels with the saved data 440. For example, the IuUP data structures of each active channel, including the RFCI table, the current TX frame number, etc., may be locally copied onto the backup module or card, such that IuUP operation may continue without notifying the remote terminal or end (e.g., the RNC). The method 400 may also include a step 450 in which the host application is also configured to not send an INIT message to the remote terminal. Two or more of the steps 430, 440 and 450 may be performed substantially simultaneously, or in sequences other than as shown in FIG. 4, as indicated by the dashed lines in FIG. 4.

In some embodiments, some incoming IuUP frames may be lost during the transition period. Also, some transmitted IuUP frames may continue from the previous frame number, although in other embodiments the transmitted IuUP frames may restart from frame number 0. The remote RNC side may also not receive frames during at least a portion of the transition period, and may resume receiving frames with some discontinuity in frame numbers. However, such as for conversational and streaming traffic classes, the frame numbers may not be transaction-based (e.g., may be time-based), such that discontinuous frame numbers may not be treated as frame loss or unexpected frame numbers. For example, discontinuous frame numbers may instead be treated as time alignment matters instead of as errors, such as when frame numbers are treated as time stamps, whereby this timing information may be employed by a channel frame loss algorithm instead of generating error events. In one embodiment, the remote RNC may not attempt to detect any discontinuities in the frame numbering, such as when it is time-based. Consequently, the RNC may pass this discontinuity directly to the handset, where it may be handled by a codec function (e.g., a vocoder). A larger time delta between consecutive packets may also be passed in some embodiments, which may result in the replay of a previous packet or insertion of silence.

One or more embodiments of the method 400 may be implemented or performed by one or more of the apparatus described above, including implementations within the media gateway 100 shown in FIG. 1, the media gateway 200 shown in FIG. 2, the state machine 300 shown in FIG. 3, or combinations of aspects thereof. In these and other implementations within the scope of the present disclosure, aspects of the method 400 and similar embodiments may allow the newly initialized channel(s) to resume operation without ever providing any indication of such to the remote terminal.

Referring to FIG. 5, illustrated is a flow-chart diagram of at least a portion of another embodiment of a method 500 according to aspects of the present disclosure. Embodiments of the method 500 include implementations for reducing the number of calls dropped when establishing the media flow of a UMTS call, including when the transport network has high packet loss rate and/or when there is race condition between the two ends.

The method 500 includes a step 505 in which an INIT message is sent from the local call end. This initiates a Negative-Acknowledgement timer in a step 510, and substantially simultaneously initiates a No-Acknowledgement timer in a step 515. Relative to conventional configurations, the Negative-Acknowledgement timer started in step 510 may be an existing timer, and the No-Acknowledgement timer started in step 515 may be an additional timer, although the reverse may also be true, or each timer may be new or additional relative to conventional configurations. The No-Acknowledgement timer may be significantly longer in duration relative to the Negative-Acknowledgement timer, such as to the extent necessary to allow sufficient time for retries when no response is received.

If any Positive-Acknowledgement message is received, as may be determined in a decisional step 520, then both timers may be stopped in a step 525, and the call may proceed in a step 530. However, if no Positive-Acknowledgement message is received, as may be determined in a decisional step 520, the method 500 continues by repeating one or more call-initialization processes, such as the re-transmission of the initialization message sent in step 505, or possibly by merely continuing to await the Positive-Acknowledgement message or another message.

For example, if any Negative-Acknowledgement message is received, as may be determined in the decisional step 535, then the No-Acknowledgement timer may be stopped in a step 540, such that only the Negative-Acknowledgement timer may be relied upon for determining how much longer call-initialization processing should be repeated, as represented by the step 545. Thus, the number of retries of call-initialization (e.g., the re-transmission of the initialization message to the remote end) may be dependent upon only the Negative-Acknowledgement timer, which is shorter in duration relative to the No-Acknowledgement timer, such that the number of retries may be fewer than if also relying upon the No-Acknowledgement timer.

However, if neither a Positive-Acknowledgement message nor a Negative-Acknowledgement message is received, as may be collectively determined by decisional steps 520 and 535, then the No-Acknowledgement timer can be relied upon for determining how much longer call-initialization processing should be repeated, as represented by the step 550. Consequently, because the No-Acknowledgement timer is longer in duration relative to the Negative-Acknowledgement timer, the likelihood of successful call set-up may be increased.

The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A method of establishing media flow for a universal mobile telecommunications service (UMTS) call between a local call instance and a remote call instance, the method comprising: transmitting an initialization message from the local call instance to the remote call instance;at the local call instance, starting, substantially simultaneously, a negative-acknowledgement timer and a no-acknowledgement timer, wherein the negative-acknowledgement timer is configured to expire after a first predetermined duration, the no-acknowledgement timer is configured to expire after a second predetermined duration, and the second predetermined duration is substantially longer than the first predetermined duration; andre-transmitting the initialization message from the local call instance to the remote call instance until the earliest of: receipt of positive-acknowledgement the remote call instance;expiration of the negative-acknowledgement timer at the local call instance if negative-acknowledgement is received from the remote call instance; andexpiration of the no-acknowledgement timer at the local call instance if neither the positive-acknowledgement nor the negative-acknowledgement is received from the remote call instance, wherein the local call instance resides on a local media gateway and the remote call instance resides on a remote radio network controller (RNC); the method further comprising: stopping the negative-acknowledgement and no-acknowledgement timers when the positive-acknowledgement is received from the remote call instance; and stopping the no-acknowledgement timer when the negative-acknowledgement is received from the remote call instance.

2. The method of claim 1 wherein re-transmitting the initialization message includes re-transmitting the initialization message at periodic time intervals.

3. A media gateway apparatus configured to support media flow of a universal mobile telecommunications service (UMTS) call between a local call instance and a remote call instance, comprising: a negative-acknowledgement timer implemented at the local call instance and being active for a first predetermined duration commencing substantially simultaneously with initial transmission of an initialization message from the local call instance to the remote call instance;a no-acknowledgement timer implemented at the local call instance and being active for a second predetermined duration commencing substantially simultaneously with the initial transmission of the initialization message, wherein the second predetermined duration is substantially greater than the first predetermined duration; andmeans for re-transmitting the initialization message from the local call instance to the remote call instance until the earliest of: receipt of positive-acknowledgement from the remote call instance;expiration of the negative-acknowledgement timer at the local call instance if negative-acknowledgement is received from the remote call instance; andexpiration of the no-acknowledgement timer at the local call instance if neither the positive-acknowledgement nor the negative-acknowledgement is received from the remote call instance, wherein the local call instance resides on the media gateway apparatus and the remote call instance resides on a remote radio network controller (RNC); wherein the negative-acknowledgement and no-acknowledgement timers are configured to be stopped upon receipt of the positive acknowledgement from the remote call instance prior to termination of either the first or second predetermined durations, and wherein the no-acknowledgement timer is configured to be stopped upon receipt of the negative-acknowledgement from the remote call instance prior to termination of the first predetermined duration.

4. The media gateway apparatus of claim 3 wherein the initialization message retransmitting means is configured to stop re-transmitting the initialization message if neither the positive-acknowledgement, the negative-acknowledgement, nor no-acknowledgement is received upon expiration of the negative-acknowledgement and no-acknowledgement timers.