EP1800453A1

EP1800453A1 - A method for routing calls in a telecommunications network

Info

Publication number: EP1800453A1
Application number: EP05801552A
Authority: EP
Inventors: Bizhan Karimi-Cherkandi; Farrokh Mohammadzadeh Kouchri
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2004-10-14
Filing date: 2005-10-07
Publication date: 2007-06-27
Also published as: WO2006040299A1

Abstract

The present invention relates to a method for routing a call in a telecommunications network and a switch for a telecommunications network. More particularly, the present invention relates to a method and telecoms switch for facilitating optimized resource allocation to calls.

Description

A Method for Routing Calls in a Telecommunications Network

This application is related to and claims the benefit of com^¬ monly-owned U.S. Provisional Patent Application No. 60/618,629, filed October 14, 2004, titled "Codec Dependent Routing" which is incorporated by reference herein in its en^¬ tirety.

The present invention relates to a method for routing a call in a telecommunications network and a switch for a telecommu^¬ nications network. More particularly, the present invention relates to a method and telecoms switch for facilitating op- timized resource allocation to calls.

Modern communications networks generally carry two types of traffic or data. The first is the traffic which is transmit^¬ ted by or delivered to a user or subscriber, and which is usually paid for by the user. That type of traffic is widely known as user traffic or subscriber traffic and usually con^¬ veyed by means of so called bearer connections, or bearers. The second is the traffic caused by network management appli^¬ cations in sending and receiving management data from network elements, known as management traffic.

In telecommunications, the management traffic is also known as signaling traffic. The term "signaling" refers to the ex^¬ change of signaling messages between various network elements such as database servers, local exchanges, transit exchanges, and user terminals.

With the advent of "next generation" packet based telecommu^¬ nications networks, and internet protocol (IP) based networks in particular, new signaling and bearer protocols were devel¬ oped by the ITU and other standards bodies such as IETF, ETSI, and 3GPP. The functional architecture of such Next Generation Networks (NGN) seeks to provide a technology independent architecture for supporting multimedia services. The intention is to sup^¬ port a wide range of voice, data and video services.

For reasons explained in more detail below, both the signal^¬ ing connection (s) and the bearer connection (s) between two pieces of network equipment may comprise more than one dis^¬ tinct path. The bearer, for example, can be routed over dif- ferent paths.

The term "different paths" as defined for the purposes of this description as paths through:

- different networks (regardless of type of network) , - different nodes within one network,

- different node elements within one node, or

- different circuits within one node element.

There may exist requirements or regulations for the network and/or its operator to select a specific path among a plural^¬ ity of choices. Examples of such requirements or regulations, and other considerations, include:

- Governmental regulation, which limits the choice of the path selection based on inter-LATA or intra-LATA proper- ties of calls through different network providers.

- Amount of call traffic which may require the unloading of calls through an alternative path or route.

- Fault tolerant systems which may choose different routes to compensate for defective paths. - Distribution of calls for optimization of equipment usage. Security and quality considerations may lead to selecting specific paths over regular paths.

- A user dialed number or other (destination) address infor¬ mation normally influences the routing of a call and therefore the selection of a path. Said routing methods however fail to optimally utilize net^¬ work and/or switch resources in modern networks providing a wide range of voice, data and video services.

It is therefore an object of the present invention to provide an improved routing method for telecommunications networks. It is another object of the present to provide an improved switch for telecommunications networks.

In accordance with the foregoing objects, there is provided by the invention a method for routing a call in a telecommu^¬ nications network, comprising the steps of:

- determining a destination in accordance with address in¬ formation of call messages; - determining at least two routes towards the destination; determining a set of capabilities for each route towards the destination;

- determining, for each route, if the set of capabilities matches the call's requirements; and - selecting the least expensive route from among the routes with matching capability sets.

The invention also provides a switch for a telecommunications network having a switching logic for executing the inventive method.

Advantageous embodiments of the invention are subject of the dependent claims .

Embodiments of the invention will now be described in more detail with reference to figures, wherein:

Fig. 1 shows in the form of a flow diagram one embodiment of the inventive method; Fig. 2 shows an exemplary network configuration wherein the invention may be deployed;

Fig. 3 shows in the form of a flow diagram the steps for con¬ figuring a switch of a telecommunications network; and Fig. 4 shows in the form of a flow diagram another embodiment of the inventive method.

Turning to Fig. 1, in step 12, a destination of a call is de- termined. Such determination may be based, for example, on address information 14 contained in call messages such as call setup messages. This address information may, in turn, be provided by a calling user (not shown) trying to set up a connection to a called user.

In step 16, at least two routes, or paths, towards the desti^¬ nation are determined. In an embodiment, the result of step 16 may be available routes, i.e., routes that are neither congested nor otherwise unavailable. In another embodiment, the number of possible routes, which may be large in certain configurations, may be limited to allow for a speedier proc^¬ essing of the results of step 16.

In step 18, the route capabilities are determined for each route that was determined in step 16. Route capabilities may include items such as: available bandwidth, available codecs for audio and/or video and/or "pure" data transmission, line and/or service quality, etc.

In step 20, the route capabilities determined in step 18 are matched, for each route, with the requirements of the call to be routed. The result of matching step 20 is a set of routes able to accommodate the call to be routed. For example, a ba^¬ sic audio call can be conveyed using any of the following routes: a route having basic audio capabilities, a route hav^¬ ing advanced audio capabilities, and a route having audio and video capabilities. A video call, on the other hand, can only be conveyed on the route having video capabilities. Thus, the outcome of step 20 will be all three routes for the basic au- dio call and only the video enabled route for the video call.

Finally, in step 22, there will be selected among the routes determined by matching step 20 the least expensive route that can accommodate the call. The "cost", or resource value, as^¬ sociated with a route may depend on several factors. Codecs, for example, may have a large impact on the cost incurred by routing a call. Expensive, or valuable, codecs may include video codecs or advanced audio codecs such as G.723 or G.729. Inexpensive codecs include, for example, audio codecs such as G.711, a codec traditionally used in voice encoding over PSTN-type telecommunications networks. The cost caused by a codec may be influenced by licensing fees for using the codec (usually charged per port supporting the codec) , and hardware requirements to support the codec (advanced video codecs, for example, require a large quantity of computing power in order to operate in real-time) .

By first selecting all routes that can accommodate a call, and then selecting the least expensive route among those, the invention achieves an optimal usage of network resources, which will be illustrated in the following preferred embodi^¬ ment of the invention.

A given gateway of the network may support a video codec and an audio codec at the same time and to the same destination. In such a gateway and using traditional routing methods, a pure audio call to that same destination may occupy the sys- tern resource, which is capable of video too. With the tradi^¬ tional method, system resources are wasted because the expen^¬ sive video codec is seized for an inexpensive (and low- revenue) audio call. This may also be true for a pure audio call: for example a G.711 to G.711 call (inexpensive codec) and a G.723 to G.711 call (expensive codec) are two different calls with regards to system resource usage.

To mitigate to problems that result from the high procurement costs of such gateway and wasted resources for the seizing duration of an inexpensive call, it had been suggested that telecommunications providers procure different gateways for different usage types, e.g., an audio-only gateway and an au^¬ dio-video gateway. This way the users are forced to use dif- ferent ways of placing their different call types. For exam^¬ ple a SIP user having audio and video capability invokes dif^¬ ferent routes for his audio calls and for his video calls by dialing different numbers.

By contrast, in the preferred embodiment of the invention, the switching logic routes the call codec dependent. As noted briefly above, the codecs are not equally expensive. There^¬ fore, codec dependent routing provides for more cost-effi- cient routing by including codec properties in the routing process. Codec-dependent routing also provides for a better resource management.

An important advantage to the user is that in the preferred embodiment the call requirements may be determined from the calling user's invoked services and not, as had been previ^¬ ously suggested, by the user dialing different numbers or otherwise providing an explicit gateway selecting address. As a result, the user may dial the same number to a given desti- nation but may activate different services for each call to that destination.

From a telecommunications provider's perspective, if a gate^¬ way is employed, the switching resources in that gateway are optimally used because inexpensive calls are routed differ^¬ ently along routes where these calls do not seize expensive resources .

In fig. 2, there is shown an exemplary network configuration 100 illustrating the application of the inventive method in a telecommunications network.

In fig. 2, an IP based network section 101, for example a SIP network, is connected via gateways 103, 104 to a TDM network section 110. Connected to the IP based network 101 is an ex^¬ emplary terminal equipment 105 having the capability to com^¬ municate using a multitude of audio codecs, including the GSM codes. A call setup message, such as a SIP INVITE message, or any other call message, will give an indication of all codecs available at terminal 105 for a given call. Such indication will be received by a soft switch 102 controlling the call.

In the example of fig. 2, two routes 106, 107 via respective gateways 103, 104 exist between a calling user at IP terminal 105 and a called user at TDM terminal 113. First gateway 103 may be a low-end (and inexpensive) gateway capable of GSM co^¬ dec transcoding, whereas second gateway 104 may be a high-end (and expensive) gateway capable of handling a vast variety of codecs such as G.723, GSM, μ-law PCM, A-law PCM, G.726, ADPCM, SLIN, LPClO, G.729, SPEEX, iLBC. Each of the routes 106, 107 is capable of connecting an audio call from IP ter¬ minal 105 to TDM terminal 113.

In accordance with the invention, soft switch 102 chooses the least expensive available route for completing a call setup from IP terminal 105, in the example of fig. 2 by choosing route 106 via first gateway 103, as IP terminal 105 supports the GSM codec which is also supported by less expensive gate^¬ way 103.

In other situations, for example if another VoIP terminal (not shown) controlled by soft switch 102 having only G.723 capability, it would be impossible to choose route 106 as first gateway 103 does not support this codec. Accordingly, soft switch 102 will choose route 107 via second gateway 104 to connect such VoIP terminal to destination terminal 113, employing the more expensive resource in the absence of an alternative, less expensive, route.

In fig. 3, there is given a flow diagram of administrative steps for configuring a switch such as soft switch 102 of telecommunications network 100. In such soft switch 102, each route 106, 107 via gateway 103, 104 to a given destination, e.g. the TDM network 110, needs to be configured. This may be accomplished by entering gateway information in step 201, en^¬ tering the gateway's supported codec types in step 202, and entering a resource value, or cost, associated with the gate^¬ way itself and/or each codec in step 203. This procedure may be repeated for each gateway available to a given destina^¬ tion. Protocol means may be provided for a soft switch to automatically detect gateways to a given destination and de^¬ termine the gateway and/or codec properties and cost.

Finally, fig. 4 shows in the form of a flow diagram another embodiment of the inventive method, preferably employed by a soft switch 102 for selecting a route towards a destination. In step 301, all available, regular routes are determined. In step 302, it will be determined if multiple routes towards the destination exist. If not, the method exits by selecting the only route for conveying the call information in step 306. Otherwise the method continues by determining in step 303 one of the available routes is marked "preferred route". If this is the case, method exits by selecting the preferred route for conveying the call information in step 307. Other¬ wise all available routes are assigned a value which is de- rived from the codec or gateway values available at each route's gateway in step 304. In step 305, the least expensive route is selected by comparing the route's values as assigned in step 304 and selecting the route having the lowest value representing the least cost.

Claims

1. A method for routing a call in a telecommunications net^¬ work (100), comprising the steps of: - determining a destination (113) in accordance with address information of call messages;

- determining at least two routes (106, 107) towards the destination (113) ; determining a set of capabilities for each route towards the destination;

- determining, for each route, if the set of capabilities matches the call's requirements; and selecting the least expensive route from among the routes with matching capability sets.

2. The method of claim 1, wherein the set of capabilities comprises media capabilities.

3. The method of claim 2, wherein the media capabilities com- prise audio and/or video codecs.

4. The method of any of the preceding claims, wherein the call's requirements are determined based on services invoked by a user and independently of a user selected destination address.

5. A switch (102) of a telecommunications network (100), com^¬ prising a switching logic configured to:

- determine a destination (113) of a call in accordance with address information of call messages; determine at least two routes (106, 107) towards the des^¬ tination (113) ;

- determine a set of capabilities for each route (106, 107) towards the destination; - determine, for each route, if the set of capabilities matches the call's requirements; and select the least expensive route from among the routes with matching capability sets.

6. The switch of claim 5, wherein the switching logic is fur¬ ther configured to determine and match media capabilities.

7. The switch of claim 6, wherein the switching logic is fur¬ ther configured to determine and match audio and/or video co^¬ decs .

8. The switch of any of claims 5 through 7, wherein the switching logic is configured to determine the call's re^¬ quirements based on services invoked by a user and independ^¬ ently of a user selected destination address.