WO1998046042A1

WO1998046042A1 - Carrier card interface to a daughter board

Info

Publication number: WO1998046042A1
Application number: PCT/US1998/007281
Authority: WO
Inventors: Serge F. Fourcand; Leo L. Nieuwesteeg; Nadar Sabzevari; Richard Schroder; William R. Cumpston; Hugh J. Scandrett; Avo Geuarkian-Livaskani; Dwight W. Doss
Original assignee: Alcatel Usa Sourcing, L.P.
Priority date: 1997-04-10
Filing date: 1998-04-09
Publication date: 1998-10-15
Also published as: EP0974241A1; JP2002511960A; ZA983051B; AU7109498A

Abstract

An interface to a daughter board includes a carrier card, a board interface connector residing on the carrier card operable to couple the daughter board to the carrier card, and a control message bus coupled between the carrier card and the daughter board. Further, the interface includes an on board controller residing on the carrier card which is in communication with the daughter board by receiving and transmitting control messages transported on the control message bus. The interface also includes a data bus adapted for transporting data between the carrier card and the daughter board, and a data bus interface coupled to the on board controller operable to transport a plurality of channels of telecommunications data to the daughter board via the data bus under the control of the on board controller.

Description

CARRIER CARD INTERFACE TO A DAUGHTER BOARD

TECHNICAL FIELD OF THE INVENTION

This invention is related in general to the field of electronic circuits, and more particularly, to a carrier card interface to a daughter board.

BACKGROUND OF THE INVENTION

In U.S. Patent No. 5,495,484 issued on Feb. 27, 1996 to Self et al . ("Self"), a distributed telecommunications switching system is disclosed. Self is incorporated herein by reference. The distributed telecommunications switch system includes a service unit (SU) coupled to one or more delivery units (DUs) . The delivery units provide the switching function and network interfaces to transmit the call information to other delivery units or other wireless or wire line networks. The service unit controls and directs each delivery unit in the switching of call information from origination to destination. The distributed telecommunications switching system can support multiple delivery units that provide a variety of services, including broadband interfacing, cable applications, telephony interfacing, and personal communications services .

Previously, because delivery units in the distributed telecommunications switching system operate and terminate- DSl level signals, external signal processors, such as echo cancelers that operate on the DSl signals, are employed to provide echo cancellation functions. However, with the introduction of delivery units that operate on higher level signals, such as OC-3 and OC-12, external echo cancelers are not a viable solution.

Additionally, it has become desirable to incorporate third party signal processing hardware, such as echo canceler circuits, into the distributed telecommunications switching system to provide added flexibility.

SUMMARY OF THE INVENTION

It has been recognized that it is desirable to provide a delivery unit that is capable of terminating optical signals, such as at the OC-3 level. It is also desirable to integrate echo canceling functionality into the 0C3 delivery unit. To provide added flexibility, a carrier card that is operable to accommodate a third party daughter board having signal processing circuits, such as echo cancelers, is provided. In one aspect of the invention, an interface to a daughter board includes a carrier card, a board interface connector residing on the carrier card operable to couple the daughter board to the carrier card, and a control message bus coupled between the carrier card and the daughter board. Further, the interface includes an on board controller residing on the carrier card which is in communication with the daughter board by receiving and transmitting control messages transported on the control message bus. The interface also includes a data bus adapted for transporting data between the carrier card and the daughter board, and a data bus interface coupled to the on board controller operable to transport a plurality of channels of telecommunications data to the daughter board via the data bus under the control of the on board controller.

In another aspect of the invention, a method of performing echo cancellation on an OC-N signal includes the steps of receiving, at a carrier card, a pulse code modulated telecommunications signal over a bus control module, and transmitting the pulse code modulated telecommunications signal to a daughter board over a serial data bus under the control of control messages transmitted between the carrier card and the daughter board. Echo cancellation is performed on the pulse code modulated telecommunications signal to generate an echo canceled signal, the echo canceled signal is transmitted over the serial data bus to the carrier card under the control of control messages transmitted between the carrier card and the daughter board.

A technical advantage of the present invention is the provision of an interface that will accept a third party manufactured digital signal processing board and connecting it into a DSO data stream on a call-by-call basis in a switching system that operates at the OC-N level.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference may be made to the accompanying drawings, in which:

FIGURE 1 is a simplified block diagram of a distributed telecommunications switching system (multi services platform) ; FIGURE 2 is a diagram of the high level OC3 architecture;

FIGURE 3 is a block diagram of the echo canceler card according to the teachings of the present invention; and FIGURE 4 is a diagram of an inheritance hierarchy of object oriented classes.

DETAILED DESCRIPTION OF THE INVENTION The purpose of the echo canceler interface according to the teachings of the present invention is to provide an interface between a third party echo canceler daughter board and an OC3 carrier card such that the daughter board can operate properly in the distributed telecommunications switching system described in Self et al .

FIGURE 1 is a simplified block diagram of a distributed telecommunications switching system 10 described in detail in Self et al . Distributed telecommunications switching system 10 includes a service unit 12 coupled to one or more delivery units 14. Delivery units 14 provide the switching function and network interfaces to transmit call information to other delivery units 14 or other wireless or wire line networks. Service unit 12 controls and directs each delivery unit 14 in the switching of call information from origination to destination.

Referring to FIGURE 2, distributed telecommunications switching system 10 may include an OC3 delivery unit 20, a service unit 22, and a DSl delivery unit 24, as shown in FIGURE 1. DSl delivery unit 24 terminates DSl level electrical signals, and OC3 delivery unit 20 terminates OC-3 level optical signals and converts them to DSO signals that can be connected to matrices 30 in DSl delivery unit 24. Previously, external DSl echo cancelers (not shown) are coupled to DSl delivery unit 24 to provide the echo cancellation function. With the introduction of OC3 delivery unit 20, it has been recognized that external echo cancelers operating directly on DSl or DSO level signals are not a viable solution. Therefore, echo cancelers should be integrated into OC3 delivery unit 20 in order to have access to DSO level signals. With an integrated echo canceler in OC3 delivery unit 20, echo cancellation may be executed on a DSO signal on a call-by-call basis. OC3 delivery unit 20 of the present invention includes an OC3 shelf 32 that has redundant optical terminating modules (OTM) 34 receiving optical signals, such as SONET OC-3 signals, from the public switched network (PSN) and converting them to electrical signals, such as STS-1 level signals, which may contain overhead data portions that have been formatted in a proprietary manner. The STS-1 signals are then transmitted to and received by synchronous transport signal modules (STSM) 36. Synchronous transport signal modules 36 are coupled to or plugged into a bus control module (BCM) 38 which is extended to an echo shelf 70. Bus control module 38 is also coupled to a number of application circuits, which may include a matrix interface circuit (MTXI) 40, tone recognition circuit 42, and high speed line trunk processor (HLTP) 44, to transmit telecommunications data thereto.

Echo shelf 70 includes one or more echo canceler cards 72 coupled to bus control module 38. Each echo canceler card 72 is operable to receive all 2,016 DSO channels in an OC-3 signal through bus control module 38. Echo canceler cards 72 may include one or more spare cards 73 for redundancy. It may be noted that all components in OC3 delivery unit 20, except echo canceler cards, include an active and a standby unit (as represented by the shadow blocks) for system redundancy and signal integrity. To provide the flexibility of enabling third party echo cancelers to function in echo canceler cards 72, a carrier card 74 is provided to host a third party echo canceler daughter board 76 as shown in FIGURE 3. Carrier card 74 supports a standard PCI (peripheral component interconnect) interface, such as CompactPCI™, for communication between an on board controller (OBC) 80 residing on carrier card 74 and a daughter board 76 coupled thereto via a PCI bridge or control message bus 84. On board controller 80 includes one or more microprocessor 81 which communicates with a microprocessor 77 residing on daughter board 76 using messages. Carrier card 74 also supports a second interface, such as SCSA (signal computing system architecture) , for the transport of isochronous data on an SCSA bus 86 coupled between a system bus interface (BIF) 82 on carrier card 74 and daughter board 76. System bus interface 82 provides the conversion between the internal system redundant buses and the SCSA interface.

When powering up, daughter board 76 disables its SCSA bus driver (not shown) until system initialization, done via PCI bridge or control message bus 84, is completed. SCSA bus 86 includes a data bus for transporting time division multiplexed (TDM) pulse code modulation (PCM) data in a bit serial manner. The SCSA data bus serial stream is divided into 1024 8.192 MHz divisions or frames. Each frame is thus 125 μs long. Because the SCSA data bus is a serial 16-bit wide bus, there are 16 PCM samples transmitted at any one time. During the 8 time divisions which constitute a serial data (SD) unit, 16 PCM samples are transmitted. An SD unit is defined as an integral, serial, consecutive 8-bit group of time divisions on the 16-bit data bus. The first 8-bit group following a frame sync is designated as SD unit 0, the second is designated as SD unit 1, etc. At least one echo canceler or signal processing circuit or device may reside on daughter board 76 mounted on carrier card 74. In the present embodiment, a minimum of 288 echo cancelers and a maximum of 384 echo cancelers may be supported by each daughter board 76. The CompactPCI'^IM interface between echo canceler daughter board 76 and carrier card 74 specifies all mechanical characteristics of daughter board 76, such as size and connectors. The purpose of the PCI Interface is to provide an industry standard interface between on board controller 80 and daughter board 76. The PCI Interface is used for processor communications between on board controller 80 and daughter board microprocessor 77. A message-based interface may be defined that provides full OAM&P (operations, administration, maintenance and provisioning) support for daughter board 76 as well as call processing interface that allows echo cancelers 83 to be used on a call-by-call basis.

The SCSA interface provides an industry standard interface between daughter board 76 and system bus interface 82 for transporting PCM data. Support for up to 768 DSO channels between daughter board 76 and system bus interface 82 may be provided, which allows daughter board 76 to support up to 384 echo cancelers 83, for example. Daughter board 76 may be configured to support a predetermined minimum number of echo cancelers and up to a predetermined maximum number of echo cancelers 83.

The interface between daughter board 76 and on board controller 80 includes a set of messages that incorporates the use of echo cancelers 83 in a call. The echo canceler parameters are communicated to an echo canceler 83 on a call-by-call basis. A functional description of this interface is provided below by defining the object classes and the operations to be supported on those object classes. A point-to-point connection is provided between daughter board 76 and on board controller 80. From the on board controller's point of view, daughter board 76 provides an echo canceler service that can be connected to a call. The software interface to daughter board 76 supports this capability. If daughter board 76 cannot support this capability, it informs on board controller 80 so that subsequent requests for service to that daughter board are rejected. Distributed telecommunications switching system 10 may then request service from other functioning echo cancelers 83.

From a maintenance point of view, on board controller

80 treats daughter board 76 as part of carrier card 74.

Failures of daughter board 76 affect the state of its associated carrier card 74. Faults on carrier card 74 may be of three types:

1. Faults isolated to carrier card 74 and not daughter board 76;

2. Faults isolated to daughter board 76; and 3. Faults isolated to either the carrier card 74 or daughter board 76. Distributed telecommunications switching system may treat all of the above faults in the same manner. A notification is generated and, if the fault is isolated to daughter board 76, the notification includes this fact. On board controller 80 may not test daughter board 76, so that fault detection of daughter board 76 is the responsibility of the daughter board itself. On board controller 80 may only routinely verify that it can properly communicate with daughter board 76. If communication with daughter board 76 is lost, carrier card 74 is removed from service and the system attempts to replace the function of the faulty card by using the spare card. Additionally, on board controller 80 may periodically reset daughter board 76 via the PCI Interface until communication is re-established.

Daughter board 76 may detect a loss of communication with on board controller 80. However, it may not initiate any type of recovery action which may disturb echo canceler cards 83 currently in use. From the distributed telecommunications switching system point of view, carrier card 74 and its daughter board 76 are a single entity. If the distributed telecommunications system craft requests removal of carrier card 74, then on board controller 80 informs daughter board 76 of this status change.

Echo cancelers 83 are assigned on a call-by-call basis. On board controller 80 may request an echo canceler 83 from daughter board 76 by issuing a CONNECT command message, for example. This command allows on board controller 80 to specify a particular echo canceler 83.

All the attributes of echo canceler 83 associated with processing the call may be included in the CONNECT command.

When daughter board 76 receives the CONNECT command it initializes the echo canceler with the specified parameters. Once connected, daughter board 76 may send an acknowledgment back to on board controller 80 with an identifier of the echo canceler within a predetermined time period. If an echo canceler 83 cannot be connected due to failure, daughter board 76 responds accordingly. If daughter board 76 has a partial failure where only a few echo cancelers failed, daughter board 76 may automatically switch the calls to available echo cancelers on the same board 76 and notify on board controller 80 for each call that has been assigned a new echo canceler 83. If daughter board 76 cannot switch the call to an idle echo canceler 83, it may place the echo canceler in a bypass mode and notify on board controller 80 for each affected call.

Object classes are defined to specify the interface between daughter board 76 and on board controller 80. On board controller 80 represents the managing system while daughter board 76 represents the managed system. Thus on board controller 80 is the manager while daughter board 76 serves the agent role. Three object classes, ecDaughterCard 90, ecSoftware

92, and ecCircuit 94, are defined to support the interface between on board controller 80 and daughter board 76. All objects inherit from a top class 96 as shown in the inheritance hierarchy diagram in FIGURE 4. ecDaughterBoard object class 90 is a class of managed objects that represent daughter board 76 from the perspective of on board controller 80. A single instance of this object class is created by daughter board 76 at daughter board initialization time. Daughter board 76 generates an object creation notification message after the instance of the ecDaughterBoard object is created and sends this notification to on board controller 80. The object creation notification message is used to notify on board controller 80 that daughter card 76 has been initialized and how many echo cancelers 83 it supports.

A state change notification message is used to inform on board controller 80 of a state change of daughter board 76. A state change may be due to an internal failure of the daughter board 76 (operational state) . An operational state of daughter board 76 informs on board controller 80 whether daughter board 76 is capable of providing echo cancellation services. An administrative state is used to support the removal and restoration of the echo canceler card from distributed telecommunications switching system 10. If an echo canceler card is to be removed from service by the distributed telecommunications switching system 10, on board controller 80 issues a SET command to the administrative state attribute. On board controller 80 may issue a GET command to obtain the operational or administrative state of daughter board 76. ecSoftware class 92 is a class of managed objects which represents the software on daughter board 76 as viewed from the perspective of on board controller 80. An instance of this object class is inherently created by daughter board 76 during initialization. An object creation notification is not generated or sent when this object is created. Class ecSoftware generates the download request notification if the underlying software represented by this object does not exist. At initialization, ecSoftware object determines if a valid load of software is present on all processors on daughter board 76. If this condition is not true, ecSoftware object generates the download request notification. If the software code is not downloaded within a predetermined time, ecSoftware object causes daughter board 76 to restart the initialization sequence. If during initialization, daughter board 76 determines that the underlying code represented by the ecSoftware object is present, it creates an instance of ecDaughterBoard object class 90. Code is downloaded via the ecSoftware object utilizing a downloadChunk action by iteratively invoking it until all code is downloaded to daughter board 76. Once the code has been downloaded, daughter board 76 verifies its checksum and continues to create an instance of ecSoftware managed object 92. If the checksum verification fails, a checksumFailure notification is generated, and the code represented by the created object is deleted. The initialization sequence is then restarted to download the software. Object ecSoftware will routinely verify its checksum after it has been created. A checksumFailure notification is generated whenever the checksum verification fails. This reinitiates the software download process. ecCircuit class 94 is a class of managed objects that represents the individual echo canceler circuits 83 on daughter board 76 from the perspective of on board controller 80. An instance of this object class is inherently created by on board controller 80 for every echo canceler circuit 83 on daughter board 76. Create notifications are not generated for this object. Object class ecCircuit 94 is used to initialize the echo canceler parameters. These parameters are provisioned with respect to a DSO level signal. When a call is made on a DSO signal that needs echo cancellation, the parameters are downloaded to the object instance of the echo canceler that will provide this function as part of a CONNECT action or command.

The attributes of ecCircuit object are set by carrier card 74 via the CONNECT command. The GET/SET commands on each attribute can also be used to change or read the value of the attribute. However, the attributes for an echo canceler 83 are valid only when the particular echo canceler is in use. An operationalState attribute is maintained by ecDaughterCard object 90 and indicates if the echo canceler circuit is operational. A usageState attribute indicates if a call is in progress on the echo canceler. This state attribute is normally idle except when a CONNECT or loopback request is received. A stateChange notification is used to indicate a change in the operational state of the echo canceler. This notification indicates whether the call was placed in the bypass mode. Daughter board 76 honors CONNECT requests except when it determines that the echo canceler failed or cannot provide the service for some reason. If daughter board 76 determines that the echo canceler is currently busy, it honors the CONNECT request but indicates this condition in the CONNECT response.

Exemplary attributes for ecDaughterCard, ecSoftware, and ecCircuit objects are summarized below with brief discussion of their functionality: • administrativeState - This attribute is used to describe the administrative state of daughter board 76 and echo canceler circuits 83. When unlocked, daughter board 76 is allowed to perform its functions. When locked, daughter board 76 may not support ACTION commands such as connectEC, disconnectEC, loopback, and releaseLoopback. This attribute is based on recommendation X.721. • availabilityStatus - This attribute is used to describe the availability status of daughter board 76. The purpose of this attribute is to indicate to on board controller 80 when daughter board 76 is partially disabled. That is, daughter board 76 has a problem that reduces its capability. This attribute is based on recommendation X.721.

• codingLa - This attribute is used to specify to echo canceler 83 what coding law should be supported for this call.

• ecCircuitld - This attribute specifies the echo canceler circuit identifier.

• ecDaughterBoardld - This attribute identifies daughter board 76 with respect to carrier card 74.

• echoReturnLoss - This attribute is used to indicate to the echo canceler what value it should use for the echo return loss (ERL) for this call. • echoReturnLossEnhancementMessageReport - This attribute is used to indicate to the echo canceler if it should generate a message to the echo canceler management system when the echo* canceler cannot meet the ERLE requirements for that call.

• maxTailSize - This attribute is used to indicate to the echo canceler what the maximum tail size should be.

• nonLinearProcessorMode - This attribute is used to indicate to the echo canceler how the non linear processor should be used for the call.

• operationalState - This attribute is used to describe the operational state of daughter board

76. When enabled, daughter board 76 is able to provide full or partial service (as indicated by the availability status) . When disabled, daughter board 76 cannot provide any service. • toneDisablerMode - This attribute is used to indicate to the echo canceler what mode the tone disabler should be set to for this call.

• reEnableMode - This attribute is used to specify what mode of operation the echo canceler re- enabler function should use for this call. This is only applicable when the toneDisablerMode is not off.

• numEcCircuits - This attribute is used to identify to the on board controller how many echo canceler circuits daughter board 76 can support.

• suppressionThresholdMode - This attribute is used to indicate to the echo canceler what type of suppression threshold to use for the call.

• suppressionThresholdValue - This attribute is used to indicate to the echo canceler what the threshold value should be for this call. This attribute is only applicable when the suppressionThresholdMode is set to the fixed- mode . • tailSizeAutoIncrement - This attribute is used to indicate to the echo canceler whether or not the echo canceler should automatically select the optimum tail size. • ToneDisablerMessageReport - This attribute is used to indicate to the echo canceler if it should generate a message to the echo canceler management system when the echo canceler detects a valid disabler tone. • h VendorName - This attribute is used to identify the vendor of the carrier card and is used for display purposes only.

• hwVersion - This attribute is used to identify the hardware version of the carrier card. It is used for display purposes only.

• swVersion - This attribute is used to identify the software version of the carrier card. It is used for display purposes only.

• swVendorName - This attribute is used to identify the vendor of the carrier card software and is used for display purposes only.

• comfortNoiseLevel - This attributes specifies the comfort noise level. This attribute is only applicable when the non-linear processor is set to OnWithComfortNoise.

• byPassMode - This attribute is used to place echo canceler into the bypass mode of operation.

• dataCollectionReport - This attribute is used to indicate to the echo canceler if it should generate a message to the carrier card with the echo canceler data information for that call. The following is a summary of exemplary notification messages and a brief description thereof: • objectCreation - This notification is required to report to on board controller 80 that an object has been created. From the point of the on board controller, only the ecDaughterCard object 90 supports this notification. The notification informs on board controller 80 that the daughter board 76 is up and running.

• stateChange - This notification is used to report to on board controller 80 when an object's state has changed. This notification is used only for operation state changes for ecDaughterCard object 90 and ecCircuit object 94.

• toneDisablerReport - This notification is used to report to carrier card 74 when an echo canceler circuit 83 is disabled because it has received a valid tone disabler message. A specific flag may be set to enable this notification.

• erleMessageReport - This notification is used to report to on board controller 80 when an echo canceler cannot achieve the required ERLE. A specific flag may be set to enable this notification.

• dataCollectionReport - This notification is used to report echo canceler data, such as ERL level, transmit power, and receive power, etc. to carrier card 74. A specific flag may be set to enable this notification.

• downloadRequest - This notification is used to report to carrier card 74 that daughter board 76 needs software to be downloaded.

• checksumFailure - This notification is used to report to carrier card 74 that daughter board detected a checksum failure on its software. The following is a list of exemplary actions that may take place:

• connectEc - This action is invoked by carrier card 74 to connect a specific echo canceler circuit on daughter board 76. When the echo canceler circuit is connected, all attributes are included as part of the action. If carrier card 74 determines that the designated echo canceler circuit is busy, then it may honor the request but indicate this condition in the connection response. The response is sent within a predetermined amount of time, for example 5 ms .

• disConnectEc - The disConnectEc service is sent from the on board controller to the daughter board 76 to disable echo cancellation on the circuit. No information is required in the response. The response shall be provided within a predetermined amount of time, for example 5 ms .

• loopbackEC - The loopback service is sent from carrier card 74 to daughter board 76 to loopback the channels. No information is required in the response. The response shall be provided within a predetermined amount of time, for example 5 ms .

• releaseLoopbackEC - This service is sent from carrier card 74 to daughter board 76 to release the loopback of the channels. No information is required in the response. The response shall be provided within a predetermined amount of time, for example 5 ms . • test - The test service is sent from carrier card

74 to daughter board 76 to test the echo canceler circuit 83.

• downloadChunk - This service provides a mechanism, for carrier card 74 to download a part of the carrier card code, which is one message lengths worth of data. This is the largest application protocol data unit supported by the size of the message buffer. There is no protocol support for segmentation and reassembly at the protocol level. Carrier card 74 breaks the file into data lengths that can be transmitted in one message and uses the downloadChunk action repeatedly until the entire file is transmitted. Therefore, a typical call establishment would entail host carrier card 74 sending a CONNECT message to daughter board 74 to identify the echo channel to be used for echo cancellation. A typical echo canceler call clearing would then entail host carrier card 74 sending a DISCONNECT message to daughter board 74 to identify the echo channel for disconnect.

As described above, the SCSA bus contains 2048 channels which can be configured to transport PCM speech samples to and from echo canceler daughter card 76. Daughter card 76 may handle 288 echo canceler channels, for example. The SCSA bus time slots are fixed for each echo channel. The SCSA time slots are assigned to the echo channels according to a predetermined assignment specification. Host carrier card 74 sends control messages to daughter board 76 over PCI bridge 84 to control the operations of the echo cancelers. The following is a description of selected control messages.

The control message set may include a CONNECT message, which includes certain information elements, such as: Message Identification, Channel Identification, PCM Encoding, Maximum Tail Delay, Automatic Tail Delay Increment, Automatic Tail Delay Increment Control, ITU Mode, Tone Disabler Mode, Tone Disabler Message Reporting Control, Switched 56K Mode, Re-Enable Mode, NLP Operating Parameters, NLP Control, Noise Matching Operating Parameters, Noise Matching Control, Minimum ERL Level, and Alarm Reporting Control. Host carrier card 74 sends this message to echo canceler daughter board 76 (ECDB) to set the channel configuration parameters to a provisional parameters set by the system. The set channel configuration parameter message is sent after initialization and when the provisional state is changed by craft personnel. These parameters over-write the default parameter values.

The control message set may also include a second type of CONNECT message, which may include most of the same information elements as the set channel configuration parameter message. Host carrier card 74 sends this message to daughter board 76 to set the echo canceler parameters and enable echo cancellation at the same time. This can be used if the echo canceler channel parameters are changed on call-by-call basis. In addition, the control message set may also include a third type of CONNECT message, which merely enables a specific echo canceler channel specified in the message. The host carrier card 74 send this message to ECDB 76 to enable echo canceler channel for normal echo cancellation processing. The echo canceler performs its function until it is told by the host to stop processing. The control message set may also include a fourth type of CONNECT message that contains the Channel Identification and the Call Type information elements. The host carrier card 74 sends this message to ECDB 76 to enable the specified echo canceler channel on a call that is already established. The echo canceler performs the normal function depending on the call type. The echo canceler performs its function until it is told by the host to stop processing. This message is used when an echo channel is switched in during a call which is in progress. Similarly, a DISCONNECT message may also be included in the control message set to disable echo canceler processing. The echo canceler in this mode performs bypass on both receive and transmit direction. The control message set may also include an ECDB initialization request message. Host carrier card 74 sends this message to ECDB 76 to request that all echo channels be initialized to their default (power-up) parameter values. Once all channels are restored an ECDB initialization complete message is sent to the host indicating successful completion of the initialization sequence.

The control message set may also include an ECDB ID inquiry message. Host carrier card 74 may send this message to ECDB 76 during initialization to know what type of daughter card it is communicating with. This is used for configuration control. The ECDB should respond to this message at any time by returning an ECDB ID report message. The ECDB ID report message includes the revision ID of the echo canceler daughter card. Further, ECDB 76 may send a predetermined key that identifies it as a valid card for the system. If the host does not recognize the key, then the daughter board is not an authorized card and will be rejected. It may be seen that messages are used to request actions to be taken (carrier card to ECDB) and notifications of events which have occurred (ECDB to carrier card) . Parameters are passed in these messages via object attributes. Exemplary attributes, actions and notifications are described above.

Although several embodiments of the present invention and its advantages have been described in detail, it should be understood that a myriad of mutations, changes, substitutions, transformations, modifications, variations, and alterations can be made therein without departing from the teachings of the present invention, the spirit and scope of the invention being set forth by the appended claims .

Claims

WHAT IS CLAIMED IS:

1. An interface to a daughter board, comprising: a carrier card; a board interface connector residing on the carrier card operable to couple the daughter board to the carrier card; a control message bus coupled between the carrier card and the daughter board; an on board controller residing on the carrier card in communications with the daughter board by receiving and transmitting control messages transported on the control message bus; a data bus adapted for transporting data between the carrier card and the daughter board; and a data bus interface coupled to the on board controller operable to transport a plurality of channels of telecommunications data to the daughter board via the data bus under the control of the on board controller.

2. The interface, as set forth in claim 1, wherein the daughter board comprises a digital signal processor.

3. The interface, as set forth in claim 1, wherein the daughter board comprises an echo canceler.

4. The interface, as set forth in claim 1, wherein the daughter board comprises a plurality of echo canceler circuits .

5. The interface, as set forth in claim 1, wherein the daughter board comprises a microprocessor in communications with the on board controller.

6. The interface, as set forth in claim 1, wherein the carrier card is coupled to a bus control module residing on a telecommunications switching system operable to transmit telecommunications data to and from the telecommunications switching system.

7. The interface, as set forth in claim 4, wherein the carrier card is coupled to a bus control module residing on a telecommunications switching system and operable to transmit at least one channel of telecommunications data to and from the telecommunications switching system, the echo canceler circuits operable to perform echo canceling function on the at least one channel telecommunications data.

8. The interface, as set forth in claim 1, further comprising a daughter board identification key contained in a control message transmitted from the daughter board to the carrier card over the control message bus, the daughter board identification key adapted to validate the daughter board.

9. The interface, as set forth in claim 4, further comprising: a daughter board object class, an instance of which is created at initialization of the daughter board; and an echo canceler object class, an instance of which is created for every echo canceler circuit on the daughter board.

10. The interface, as set forth in claim 9, further comprising an echo canceler software object class representative of a software load on the daughter board, an instance of the echo canceler software object being created at initialization of the daughter board.

11. The interface, as set forth in claim 1, further comprising an initialization request message sent from the carrier card to the daughter board to initialize the daughter board.

12. The interface, as set forth in claim 4, further comprising an initialization request message sent from the carrier card to the daughter board to initialize the echo canceler circuits on the daughter board.

13. The interface, as set forth in claim 4, further comprising a set channel configuration parameters message sent from the carrier card to the daughter board to set the echo channel configuration parameters to predetermined values .

14. The interface, as set forth in claim 4, further comprising a set parameters & enable echo cancellation message sent from the carrier card to the daughter board to set the echo channel configuration parameters to predetermined values and enable echo cancellation.

15. The interface, as set forth in claim 4, wherein the data bus comprises a set of serial data streams transmitting echo canceling channels for the echo cancellation circuits on the daughter board.

16. A telecommunications switch operating on optical signals, comprising: a switch; a carrier card; a bus control module residing on the switch and operable to transmit at least one channel of telecommunications data between the switch and the carrier card; a daughter board having a plurality of digital processing circuits; a board interface connector residing on the carrier card operable to couple the daughter board to the carrier card; a data bus adapted for transporting the telecommunications data between the carrier card and the daughter board; a control message bus coupled between the carrier card and the daughter board; an on board controller residing on the carrier card in communications with the daughter board by receiving and transmitting control messages transported on the control message bus; and a data bus interface coupled to the on board controller operable to transport the telecommunications data to the daughter board via the data bus under the control of the on board controller.

17. The telecommunications switch, as set forth in claim 16, wherein the daughter board comprises a plurality of echo canceler circuits.

18. The telecommunications switch, as set forth in claim 16, wherein the daughter board comprises a microprocessor in communications with the on board controller.

19. The telecommunications switch, as set forth in claim 16, further comprising a daughter board identification key contained in a control message transmitted from the daughter board to the carrier card over the control message bus, the daughter board identification key adapted to validate the daughter board.

20. The telecommunications switch, as set forth in claim 16, further comprising: a daughter board object class, an instance of which is created at initialization of the daughter board; and an echo canceler object class, an instance of which is created for every echo canceler circuit on the daughter board.

21. The telecommunications switch, as set forth in claim 20, further comprising an echo canceler software object class representative of a software load on the daughter board, an instance of the echo canceler software object being created at initialization of the daughter board.

22. The telecommunications switch, as set forth in claim 16, further comprising an initialization request message sent from the carrier card to the daughter board to initialize the daughter board.

23. The telecommunications switch, as set forth in claim 16, further comprising an initialization request message sent from the carrier card to the daughter board to initialize the echo canceler circuits on the daughter board.

24. The telecommunications switch, as set forth in claim 16, further comprising a set channel configuration parameters message sent from the carrier card to the daughter board to set the echo channel configuration parameters to predetermined values .

25. The telecommunications switch, as set forth in claim 16, further comprising a set parameters & enable echo cancellation message sent from the carrier card to the daughter board to set the echo channel configuration parameters to predetermined values and enable echo cancellation.

26. The telecommunications switch, as set forth in claim 16, wherein the data bus comprises a set of serial data streams transmitting echo canceling channels for the echo cancellation circuits on the daughter board.

27. A method of performing echo cancellation on an OC-N signal, comprising the steps of: receiving, at a carrier card, a pulse code modulated telecommunications signal over a bus control module; transmitting the pulse code modulated telecommunications signal to a daughter board over a serial data bus under the control of control messages transmitted between the carrier card and the daughter board; performing echo cancellation on the pulse code modulated telecommunications signal and generating an echo canceled signal; and transmitting the echo canceled signal over the serial data bus to the carrier card under the control of control messages transmitted between the carrier card and the daughter board.

28. The method, as set forth in claim 27, further comprising the step of verifying the validity of the daughter board by sending a control message containing a daughter board identifying key from the daughter board to the carrier card.

29. The method, as set forth in claim 27, further comprising the step of initializing the daughter board by sending an initializing control message from the carrier card to the daughter board.

30. The method, as set forth in claim 27, further comprising the steps of: sending an enable echo cancellation circuit control message from the carrier card to the daughter board; and enabling an echo cancellation circuit in response to the enable echo cancellation circuit control message.

31. The method, as set forth in claim 27, further comprising the steps of: sending a disable echo cancellation circuit control message from the carrier card to the daughter board; and disabling an echo cancellation circuit in response to the enable echo cancellation circuit control message.

32. The method, as set forth in claim 27, further comprising the steps of: sending a set echo cancellation parameters control message from the carrier card to the daughter board; and setting the echo cancellation circuit in response to the set echo cancellation parameters control message.

33. The method, as set forth in claim 27, further comprising the steps of: sending a connect echo cancellation circuit control message from the carrier card to the daughter board; and connecting an echo cancellation circuit in response to the connect echo cancellation circuit control message.

34. The method, as set forth in claim 27, further comprising the steps of: sending a disconnect echo cancellation circuit control message from the carrier card to the daughter board; and disconnecting an echo cancellation circuit in response to the disconnect echo cancellation circuit control message.