Signal processing method for achieving per-call control

Technical Field

0001This invention relates to a technique for providing different types of enhancements to telephone calls on a call-by-call basis.

Background Art

0002To meet its customer needs and to differentiate its products and services, AT&T enhances the quality of selected voice calls carried through its inter-exchange network. Once such enhancement currently available is AT&T True Voice®service, whereby selected frequencies of a voice call are amplified to provide a more pleasing telephone conversation. The manner in which such frequencies are amplified is described and claimed in U.S. Patents 5,195,132 and 5,333,195, both entitled "Telephone Network Speech Signal Enhancement", filed in the name of Dune Bowker et al. and both assigned to AT&T (herein incorporated by reference). Another enhancement available from AT&T is compensation for background noise described in U.S. Patents 5,524,148, and 5,485,515, both entitled "Background Noise Compensation in a Telephone Network", filed in the name of Jonathan B. Allen et al. and both assigned to AT&T (herein incorporated by reference). Yet another enhancement provided by AT&T is echo cancellation obtained by routing calls through an echo canceled of a type known in the art.

0003While the above-described enhancements are useful, they can interact with existing technology, and in some instances, actually impede transmission quality. Presently, calls that require that the enhancement and/or echo cancellation be turned off are routed over separate "overlay" networks. Figure 1 illustrates the use of dedicated "overlay" networks to provide specific transmission signal processing, wherein dedicated trunking and tandem switching is implemented to provide specific transmission capabilities. Normally, voice calls are provided echo cancellation and the True Voice® enhancement, wherein the associated transmission signal, processing is provided on trunks denoted as TV on trunks. However, for calls not requiring the TV on signal processing, the dedicated overlay networks illustrated in Figure 1a need to be used. For example, as shown in Figure 1a, Switched Digital Service (SDS) data-type calls are routed through switching systems within the AT&T's network that turn off the enhancement and echo cancellation. Similarly, those voice and voice band calls requiring echo cancellation but also requiring that the voice enhancement be turned off are typically routed to dedicated via switching systems that provide echo cancellation but have the voice enhancements turned off for both incoming and outgoing trunks. While providing a specialized network to carry calls without enhancement and/or echo cancellation overcomes the problem of undesirable interactions, this approach affords little flexibility in terms of enhancing and/or performing echo cancellation on selected calls within a common network and leads to network capacity inefficiencies because of the need to provide separate dedicated networks for different types of calls, rather than using a single integrated network with a signal processing system (SPS) capability to provide the required transmission processing on a per-call-control (PCC) basis..

0004Thus, there is a need for a technique for routing calls to enable enhancement and/or echo cancellation of calls on a selected basis.

Brief Summary of the Invention

0005Briefly, in accordance with the invention, a method is provided for routing at least one call in a telecommunications network from an Originating Switching System (OSS), at which the call originates in the network to a Terminating switching System (TSS), at which the call terminates such that the call is selectively enhanced. As illustrated in Figure 1b, the dedicated overlay networks can be replaced by an integrated network capability, which consists of trunks that are provided a signal processing system (SPS) capability at the originating switching system (OSS), via switching system (VSS), and terminating switching system (TSS), to provide the desired transmission signal processing on a per-call-control (PCC) basis. These trunks are denoted as SPS per-call-control (SPCC) trunks. SPCC trunks can be used to provide, on a per-call-control basis, the required transmission signal processing, such as (a) echo cancellation with the True Voice® enhancement turned on, denoted as TV on, which could be used for normal voice calls, (b) echo cancellation with the True Voice® enhancement turned off, denoted as TV off, which could be used for example for some voiceband data calls, or (c) no-echo cancellation, denoted as EC off, which could be used for example for switched digital services (SDS) calls.

0006The method of the invention is commenced by receiving an incoming call at the OSS. For each incoming call, the OSS establishes a Circuit Selection Capability Indicator (CSCI) that specifies the type of enhancement, if any, to be provided for the call. For example, the call may be enhanced by performing echo cancellation. In place of such echo cancellation (or in addition thereto), the call may be enhanced by amplifying certain frequencies. Additionally, the call may be enhanced by compensating for background noise. Using the CSCI, the OSS selects one of a plurality of trunks interconnecting the OSS and TSS for routing the call to the TSS which could be either a direct trunk to the TSS, or on a via path through a VSS to the TSS. Based on the CSCI, the OSS performs the selected enhancement, if required. Thus, for example if the CSCI established by the OSS specifies no echo cancellation and no selective frequency enhancement, then the selected trunk can be an SPCC trunk, which can be used to provide, on a per-call-control basis, the required transmission signal processing, which in this case is no echo cancellation, denoted as EC off. Conversely, if the CSCI established by the OSS specifies call enhancement, then a trunk having the capacity to carry such enhanced calls can be an SPCC trunk, which can be used to provide, on a per-call-control basis, the required transmission signal processing, which in this case is echo cancellation with the True Voice® enhancement turned on, denoted as TV on. If such an SPCC trunk is not available, the call can be routed as a second choice option on the TV on trunks illustrated in Figure 1b, which are provisioned with echo cancellation and with the True Voice® enhancement turned on. Once the trunk is selected, the call is routed on the selected trunk for routing to the TSS where the call is enhanced in accordance with the established CSCI.

0007Hence the SPCC concept allows different types of calls which are routed on the same trunk to get different call quality enhancements (such as True Voice® and Echo Control), depending on the call type. SPCC allows a call quality enhancement to be applied to an individual call on a per call basis. SPCC allows up to 16 different types of enhancements to be applied on a call, and these enhancements can be different at the OSS and TSS, which could give different types of enhancements to the calling party and called party. With this arrangement, new signal processing "sound flavors" (enhancements), for example, could be developed on the SPS, and these new sound flavors can be offered as a new service feature through table updates in the switching system, without software development. Moreover, SPCC allows the capability to change the current enhancement for any call type to any desired enhancement through provisioning of a CSCI Table, without new switching system development.

0008The SPCC concept provides an evolutionary path for current overlay networks implemented for specialized signal processing requirements, in particular the dedicated TV off network for True Voice® enhancement avoidance, and the dedicated ECoff network to avoid echo cancellation for example for SDS services. This is achieved for these services by replacing the dedicated TVoff and ECoff trunks terminating on the switch with SPCC trunks having SPS per-call-control capability. The PCC capability of SPCC trunks allows the control of the TV Enhancement and the Echo Cancellation on a per call basis, thereby allowing the SPCC trunks to be used in a shared manner for calls requiring TV enhancement, calls requiring TV enhancement avoidance, and for data calls requiring no echo cancellation. The benefits are a) a very flexible per-call-control capability within a single integrated network, b) cost effectiveness, c) robustness to load surges, and d) improved network efficiency.

0009The above-described method advantageously provides enhancement of calls on a selected basis while also permitting non-enhanced calls to be routed between switching systems on a single, integrated network with SPCC capability, rather than requiring the use of separate networks.

Brief Summary of the Drawing

0010<ul id="ul0001" list-style="none" compact="compact"><li>FIGURE 1 is a block schematic diagram of a telecommunications network before and after the application of the invention; and</li><li>FIGURE 2 is a block schematic diagram of a telecommunications network in accordance with the invention.</li></ul>

Detailed Description

0011Figure 1a illustrates the use of dedicated "overlay" networks to provide specific transmission signal processing, wherein dedicated trunking and tandem switching is implemented to provide specific transmission capabilities. Normally, voice calls are provided echo cancellation and the True Voice enhancement, wherein the associated transmission signal processing is provided on trunks denoted as TV on trunks. However, for calls not requiring the TV on signal processing, the dedicated overlay networks illustrated in Figure 1a need to be used. For example, as shown in Figure 1a, SDS data-type calls are routed from OSS 12₁ to TSS 12₂ through a partly dedicated via switching system VSS 12₅, in which trunks 20₆ are provisioned with EC off. Similarly, calls which need to avoid the True Voice® enhancement, such as some voice band data-type calls, are routed from OSS 12₁ to TSS 12₂ through a dedicated via switching system VSS 12₄, in which trunks 20₅ are provisioned with TV off.

0012Figure 1b illustrates the use of the signal processing system SPS 24 per-call-control network to provide transmission signal processing on a per-call demand basis in accordance with the invention. Here the SPS per-call-control trunks 20₄ can provide TV on, TV off, and EC off on a per call basis. For example, as shown in Figure 1b, SDS data-type calls are routed from OSS 12₁ to TSS 12₂ either on a direct SPCC trunk 20₄, or through a via switching system VSS 12₃, in which SPCC trunks 20₄ are set to EC off. Similarly, calls which need to avoid the True Voice® enhancement, such as some voice band data-type calls, are routed from OSS 12₁ to TSS 12₂ either on a direct SPCC trunk 20₄, or through a via switching system VSS 12₃ , in which SPCC trunks 20₄ are set to TV off. Normal voice calls are provided echo cancellation and the True Voice® enhancement, and are routed from OSS 12₁ to TSS 12₂ either on a direct SPCC trunk 20₄, or through a via switching system VSS 12₃, in which SPCC trunks 20₄ are set to TV on. If SPCC trunks are not available, these normal voice calls can be routed on trunks 20₁ which are provisioned with TV on.

0013FIGURE 2 depicts a block schematic diagram of an Inter-Exchange Carrier network 10, such as the type of network maintained by AT&amp;T. In its simplest form, the network 10 includes a first toll switching system 12₁, typically a model 4ESS Toll Switch, formerly manufactured by AT&amp;T. For purposes of discussion, the switching system 12₁ will hereinafter be referred to as an "Originating Switching System " (OSS) because calls are presumed to originate (i.e., enter the network 10) at this switching station. Such calls may be received on one of a set of trunks in a trunk group 13₁ from a Local Exchange Carrier (LEC) central office switching system 14₁ serving a calling party 16₁. In practice, the LEC central office switching system 14₁ may comprise a model 5ESS switch formerly manufactured by AT&amp;T. Calls may also be received at the toll switching system 12₁ on one or more trunks in a trunk group 17₁ from a customer directly served by the switching system, such as PBX 18₁.

0014Calls originating at the OSS 12₁ terminate at a second (terminating) Toll Switching System (TSS) 12₂ coupled to the OSS via a plurality of trunks 20₁-20₄. The OSS 12₁ is also linked to the TSS 12₂ via a signaling system 22, such as AT&amp;T's Common Channel Signaling System 7 as is well known in the telephony art. Calls terminating at the toll switching system 12₂ are ultimately delivered on a trunk group 13₂ to a LEC central office switching system 14₂ for receipt by a called party 16₂ or on a trunk group 17₂ to customer directly served by the TSS, such as PBX 18₂. While the network 10 has been depicted as including a single OSS 12₁ and single TSS 12₂, a typical IXC network, such as that maintained by AT&amp;T, includes a plurality of interconnected toll switching systems, including those which originate and terminate calls, as well as via switching systems that interconnect such originating and terminating switching systems.

0015Both of the switching systems 12₁ and 12₂ possess a Signal Processing System (SPS) 24 associated with a time-slot interchanger (not shown) within each of the switching systems 12₁ and 12₂. The SPS 24 within each switching system may have echo cancellation capability, the ability to amplify selected frequencies as described in the Bowker et al. patents 5,195,132 and 5,333,195 (herein incorporated by reference) (AT&amp;T True Voice® voice enhancement), and/or the ability to compensate for background noise as described in the Allen et al. patents 5,524,148, and 5,485,515 herein incorporated by reference. The ability of the SPS 24 to enhance voice calls is very advantageous. However, for certain types of calls, such as data calls, for example, enhancement by echo cancellation, frequency amplification and/or background noise compensation is undesirable. To avoid enhancement of certain calls that may be undesirable, the present invention provides selective enhancement on a call-by-call basis as well as routing of calls from the OSS 12₁ to the TSS 12₂ via one of the trunks 20₁-20₄ selected in accordance with its ability to carry enhanced or non-enhanced calls as the case may be.

0016To provide for selective enhancement on a call-by-call basis, the OSS 12₁, upon receipt of an incoming call, establishes a Circuit Selection Capability Indicator (CSCI) for the call. The CSCI specifies whether the call should be enhanced, and if so, what type of enhancement should be made. For certain calls, such as data calls, for example, no enhancement should be made whereas for most voice calls, echo cancellation, frequency amplification and/or background noise cancellation may be desirable. The OSS 12₁ establishes the CSCI to activate the time slot interchanger to turn on or off the SPS 24 to provide the desired enhancement based on certain "triggers", that is, certain conditions. Generally, the triggers that dictate the CSCI for a particular incoming call are determined from one or more of the following: (1) the called number (i.e., the digits associated with the call), (2) the ANI of the calling party, (3) the nature of the trunk on which the call arrived at the OSS 12_1, (4) call processing information relayed to the OSS 12₁ from a Network Control Point (NCP) (i.e., a database) via the signaling system 22, and/or (5) the Service Indicator (SI) established for the call by the OSS 12₁ based on the nature of the call class-of-service.

0017Table I lists an exemplary set of different enhancements for various CSCI values <tables id="tabl0001" num="0001"><table frame="all"><title>TABLE I</title><tgroup cols="3" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">CSCI</entry><entry namest="col2" nameend="col2" align="left">OSS 12₁</entry><entry namest="col3" nameend="col3" align="left">TSS 12₂</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="right">0</entry><entry namest="col2" nameend="col2" align="left">TV ON, EC ON</entry><entry namest="col3" nameend="col3" align="left">TV ON, EC ON</entry></row><row><entry namest="col1" nameend="col1" align="right">1</entry><entry namest="col2" nameend="col2" align="left">TV OFF, EC OFF</entry><entry namest="col3" nameend="col3" align="left">TV OFF. EC OFF</entry></row><row><entry namest="col1" nameend="col1" align="right">2</entry><entry namest="col2" nameend="col2" align="left">TV OFF, EC ON</entry><entry namest="col3" nameend="col3" align="left">TV OFF, EC ON</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="right">3</entry><entry namest="col2" nameend="col2" align="left">TV OFF, EC ON</entry><entry namest="col3" nameend="col3" align="left">TV OFF, EC ON</entry></row></tbody></tgroup></table></tables>

0018Table I presumes two enhancements TV (AT&amp;T's True Voice® Service that provides selected frequency amplification) and EC (echo cancellation). (Other types of enhancement are possible and different CSCI values will be associated therewith.) Note that two different CSCI values (2, 3) appear to be associated with the same two enhancement states. TV OFF and EC ON. In actuality, a CSCI value of 2 reflects a condition where a TV-less enhancement is <i>required</i>, whereas a CSCI value of 3 reflects a condition where a TV-less enhancement is desired but not required.

0019The nature of the enhancement dictated by the CSCI value established at the OSS 12₁ also dictates the selection of the particular one of the trunks 20₁-20₄ connecting the OSS 12₁ and the TSS 12₂. In the illustrated embodiment of FIG. 2 each of the trunks 20₁-20₄ has different characteristics. Trunks 20₁ and 20₂ are designed to handle calls enhanced by the AT&amp;T True Voice®service, as discussed above, whereas the trunks 20₃ and 20₄ comprise a new type of trunk, hereafter designated as an SPCC trunk, whose characteristics are set via the SPS associated with the time slot interchangers of the SPCC trunk within the OSS 12₁ and the TSS 12₂. Physically, the trunks 20₃ and 20₄ are the same as the other trunks. What differentiates the trunks 20₃ and 20₄ is the characteristics of the trunks, in terms of their ability to carry enhanced, non-enhanced echo controlled or non-echo controlled calls, as determined by the OSS 12₁ and the TSS 12₂ on an call-by-call basis, depending on the CSCI for the call in which the SPS 24 associated with the SPCC trunk is controlled accordingly.

0020The manner in which the trunks 20₁-20₄ are selected is determined by mapping the CSCI values established in Table I to a Circuit Selection Capability (CSC) preference as shown below in Table II, denoted as the CSCI table. <tables id="tabl0002" num="0002"><table frame="all"><title>Table II</title><tgroup cols="8" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="19.68mm" /><colspec colnum="2" colname="col2" colwidth="19.68mm" /><colspec colnum="3" colname="col3" colwidth="19.68mm" /><colspec colnum="4" colname="col4" colwidth="19.68mm" /><colspec colnum="5" colname="col5" colwidth="19.68mm" /><colspec colnum="6" colname="col6" colwidth="19.68mm" /><colspec colnum="7" colname="col7" colwidth="19.68mm" /><colspec colnum="8" colname="col8" colwidth="19.68mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" rowsep="0" align="center">CSC</entry><entry namest="col2" nameend="col3" align="left">PCC Treatment</entry><entry namest="col4" nameend="col4" rowsep="0" align="center">FITR Treatment</entry><entry namest="col5" nameend="col7" align="center">CSCI Table CSC Preference</entry><entry namest="col8" nameend="col8" rowsep="0" align="center">Overflow CSCI</entry></row><row><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="left">OSS</entry><entry namest="col3" nameend="col3" align="left">TSS</entry><entry namest="col4" nameend="col4" /><entry namest="col5" nameend="col5" align="left">TV-less</entry><entry namest="col6" nameend="col6" align="left">SPCC</entry><entry namest="col7" nameend="col7" align="center">Other</entry><entry namest="col8" nameend="col8" /></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="right">0</entry><entry namest="col2" nameend="col2" align="left">Default</entry><entry namest="col3" nameend="col3" align="left">Default</entry><entry namest="col4" nameend="col4" align="left">Allowed</entry><entry namest="col5" nameend="col5" align="left">Abs PFI</entry><entry namest="col6" nameend="col6" align="left">Pres PFI</entry><entry namest="col7" nameend="col7" align="left">D/C</entry><entry namest="col8" nameend="col8" /></row><row><entry namest="col1" nameend="col1" align="right">1</entry><entry namest="col2" nameend="col2" align="left">Default</entry><entry namest="col3" nameend="col3" align="left">Default</entry><entry namest="col4" nameend="col4" align="left">Prohibited</entry><entry namest="col5" nameend="col5" align="left">D/C</entry><entry namest="col6" nameend="col6" align="left">Pres PFI</entry><entry namest="col7" nameend="col7" align="left">D/C</entry><entry namest="col8" nameend="col8" /></row><row><entry namest="col1" nameend="col1" align="right">2</entry><entry namest="col2" nameend="col2" align="left">TV off EC on</entry><entry namest="col3" nameend="col3" align="left">TV off EC on</entry><entry namest="col4" nameend="col4" align="left">Prohibited</entry><entry namest="col5" nameend="col5" align="left">Pres Req</entry><entry namest="col6" nameend="col6" align="left">Pres PFI</entry><entry namest="col7" nameend="col7" align="left">D/C</entry><entry namest="col8" nameend="col8" align="right">3</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="right">3</entry><entry namest="col2" nameend="col2" align="left">TV off EC on</entry><entry namest="col3" nameend="col3" align="left">TV off EC on</entry><entry namest="col4" nameend="col4" align="left">Prohibited</entry><entry namest="col5" nameend="col5" align="left">Pres PF2</entry><entry namest="col6" nameend="col6" align="left">Pres PF1</entry><entry namest="col7" nameend="col7" align="left">D/C</entry><entry namest="col8" nameend="col8" /></row></tbody></tgroup></table></tables>

0021The terms "Abs" stands for absence, "Pres" for present, "Req" for required, "PF1" for 1st preferred, "PF2" for second preferred and "D/C" for don't care. The term "default" under Per-Call Control (PCC) treatment indicates that the echo cancellation and selective frequency amplification (AT&amp;T's True Voice® service) should be on for voice calls and off for SDS (data) calls. As may be appreciated from Table II, a CSCI value of 2 indicates that the selective frequency amplification should be off and the echo cancellation should be on both at the OSS 12₁ and at the TSS 12₂. As shown in Table II, there is a, Forced Inter-Toll Routing option whereby an intra-switching system call can receive forced inter-toll routing treatment, depending on the CSCI value.

0022A set of CSC preference rules are utilized by the OSS 12₁ in selecting the particular one of trunks 20₁-20₄ over which to route calls. The degree to which trunks are selected is based on the following preference order:<maths id="math0001" num=""><math display="block"><mrow><mtext>Required > 1st Preferred (PF1) > 2nd Preferred (PF2) > Don't Care (D/C)</mtext></mrow></math><img file="EP0884884A2_D0001.tif" /></maths> For example, a call with a CSCI value of 2 requires a TV-less, "Presence Required" and "SPCC, Presence 1st Preferred" routing. In other words, a call having a CSCI value of 2 requires routing on a trunk for which TV-less = yes, and a first preference for the SPCC trunk (which is set using the SPS per-call control for TV off and EC on). In terms of trunk preference, the OSS 12₁ will hunt for a trunk in the following order: <ul id="ul0002" list-style="none" compact="compact"><li>1. TV-less = yes and SPCC = yes</li><li>2. TV-less = yes and SPCC = no</li></ul> If the OSS 12₁ seizes an idle trunk and the trunk is TV controllable with SPS per-call control capability, then the SPCC is done for the call, and under such circumstances, the call will be enhanced by echo cancellation but not by selective frequency amplification (i.e., TV off). If via routing is necessary (i.e., the call must be routed from the OSS 12₁ to the TSS 12₂ through an intermediate or via switch, (as shown in Figure 1b), then the VSS uses the CSCI indicator to select the trunk over which the call is routed from the VSS to TSS as first choice an SPCC trunk, and if selected the SPS function is used to turn the True Voice enhancement off on the SPCC trunk. If an SPCC trunk is not available, the VSS selects as second choice a trunk which has the True Voice enhancement provisioned off (TV off trunk), if such a trunk is available. Should such via routing fall, then the call is overflowed, whereby the CSCI value becomes 3. Once the call does reach the TSS 12₁, the call is treated as if the CSCI were 2 and the appropriate enhancements are made.

0023The foregoing discloses a technique for routing calls between an Originating Switching System 12₁ and a Terminating Switching System 12_2, whereby calls are selectively enhanced on a call-by-call basis in accordance with a Circuit Selection Capability Indicator established by the Originating Switching System. The CSCI value is also utilized by the Originating Switching System in selecting a trunk to the Terminating switching system that is compatible with the selected type of enhancement.

0024It is to be understood that the above-described embodiments are merely illustrative of the principles of the invention. Various modifications and changes may be made thereto by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

0025Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claim and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.