Voice Enhancement / Echo Cancellation Chip

Solutions by Adaptive Digital

VQE-168 CHIP

DESCRIPTION

The Adaptive Digital Technologies high-density voice enhancement/echo canceller chip (VQE-168) a carrier-class ITU G.168-2002 compliant PCM network echo canceller chip. This solution is based upon Adaptive Digital’s AT&T certified soft echo canceller running on the Texas Instruments TMS320C641X digital signal processor. The VQE-168 supports both T-1 and E-1 configurations.

The VQE-168 uses two TDM serial ports, one for the receive side of the canceller and the other for the send side of the canceller. The TDM serial ports are fully programmable to allow connection to nearly any type of serial bus.

The VQE-168 includes Adaptive Digital’s proprietary voice quality enhancement algorithms including noise reduction and automatic level control. These features, in conjunction with the echo canceller, ensure maximum voice quality.

FEATURES

  • EC FEATURES

  1. Certified by AT&T Voice Quality Lab
  2. ITU G.168-2002 Compliant
  3. Compliant using all ITU hybrid models
  4. Low Throughput Delay (500 microseconds)
  5. Supports up to 240 channels
  6. Adaptive Non-linear processor
  7. Comfort Noise Generator
  8. Operates in SS-7 Networks
  9. No divergence due to double-talk
  10. G.164/G.165 Tone Disabler

  • ADDITIONAL VQE FEATURES

  1. Noise Reduction
  2. Programmable “Aggressiveness”
  3. Adapts to background noise continuously
  4. Automatic Level Control
  5. Programmable maximum gain/loss
  6. Programmable Output Target Level

In order to interface to a wide variety of serial TDM busses, the VQE-168 serial port configuration is programmable. Table 1 below describes the serial port configuration parameters.

CHANNEL DENSITY
Echo Canceller
Echo Canceller with Noise Reduction and Automatic Level Control
T-1 Spans
E-1 Spans
T-1 Spans
E-1 Spans
32 msec. tail
9
7
4
3
64 msec. tail
7
6
3
2
128 msec. tail
5
4
2
2
EC Off
N/A
N/A
6
4

Note that the tail length affects the channel density of the chip.
Table: 1

Control of the VQE-168 is facilitated by using an ANSI “C” set of API functions that are provided to run on the host processor. These functions configure and control the VQE-168 as well as return status information to the host application.

Chip Configuration

The VQE-168 needs to be configured at power up. Configuration parameters for the serial ports, echo canceller, automatic level control, and noise reduction are described in the sections that follow.

Serial Port Configuration

The VQE-168 can operate using either one or two TDM serial ports. Although time slot mapping can be done, there are default time slot mappings for both the single port and the two port configurations. If two serial ports are used (ports 0 and 1), a single echo canceller channel operates on a given time slot on both serial ports. For example, echo canceller channel 0 is connected to serial port 0, time slot 0 for its receive side and it is connected to serial port 1, time slot 0 for its send side. If a single serial port is used, the receive and send sides use even and odd time slots. In this case, the receive side would be connected to serial port 0, time slot 0 and the send side would be connected to serial port 0, time slot 1

Echo Canceller Configuration Parameters
PARAMETER
VALID RANGE
DEFAULT VALUE
Global Echo Canceller Enable
Enabled/Disabled
Enable
Tail Length
32, 64, and 128 milliseconds
128
NLP Type
Off, Mute, Random Noise, or Hoth Noise
Hoth Noise
NLP Threshold
12, 18, 24 dB
24
CNG Threshold
-40..-60 dBm
-43 dBm
Double TalkThreshold
0 to 12 (units of dB)
4
G.165 Detect Enable
Enable or Disable
Enable
Adapt Enable
Enable or Disable
Enable
Number of reflectors
1 to 3 - The initial value can not be exceeded at run time.
3
Reflector Length
4, 8, 12, 16 milliseconds
8

 

Table 2: Echo Canceller Configuration Parameters

Serial Port Characteristics
PARAMETER
VALID RANGE
DEFAULT VALUE
Serial Port 0
Enabled/Disabled
Enabled
Serial Port 1
Enabled/Disabled
Enabled
Number of Time Slots
0..255
128
Use Standard Mapping
True / False
True
Data Format
u-Law, A-Law, 8 bit Linear, or 16 bit Linear
u-Law
Transmit Sync Polarity
Active High or Active Low
Active High
Receive Sync Polarity
Active High or Active Low
Active High
Transmit Clock Polarity
Rising Edge or Falling Edge
Rising Edge
Receive Clock Polarity
Rising Edge or Falling Edge
Falling Edge
Transmit Data Delay
0 to 2
1
Receive Data Delay
0 to 2
1
DX Pin Delay
Enable or Disable
Disable

Table 3: Serial Port Characteristics.

Echo Canceller Configuration

The echo canceller algorithm has numerous programmable options to allow it to be configured appropriately for a wide variety of applications. When bi-directional cancellation is selected, the canceller is independently programmable in each direction. Table 2 lists the echo canceller configuration parameters.

Automatic Level Control Configuration

Table 4 lists the configuration parameters that control the operation of the Automatic Level Control (ALC) feature.

ALC Configuration Parameters
PARAMETER
VALID RANGE
DEFAULT VALUE
Global ALC Enable
Enabled/Disabled
Enable
Target Power
-30 to 0 (units of dBm)
-18
Loss Limit
-23 to 0 (units of dB)
-10
Gain Limit
0 to 23 (units of dB)
10

Table 4 lists the configuration parameters that control the operation of the Automatic Level Control (ALC) feature.

Echo canceller channels are turned on and off as needed under control of a host processor. Each time a channel is turned on, it is necessary to provide call setup information. Since an echo canceller is a two port device, we define the two ports as side A and side B. The canceller can be configured to cancel echo in neither, one, or both directions.

If echo cancellation is enabled at the A side, the echo perceived by the speaker at the B side will be cancelled. If echo cancellation is enabled at the B side, the echo perceived by the speaker at the A side will be cancelled.

Channel Setup Parameters
PARAMETER
VALID RANGE
DEFAULT VALUE
A Side Serial Port
0.1
A Side Time Slot
0..255
B Side Serial Port
0.1
B Side Time Slot
0..255
Enable A Side EC
Enable/Disable
Enable
Enable B Side EC
Enable/Disable
Disable

Table 5: Channel Setup Parameters

If the VQE-168 is configured for standard serial port mapping, the B-side time slot will be derived from the A side time slot.

Online Control and Status Reporting

In order to perform diagnostics and testing, a number of controls are provided to modify the state of an active channel. Table 6 lists the features that be controlled during an active call. Table 7 lists the status parameters that are available during an active call.

Channel Control Parameters
PARAMETER
VALID RANGE
DEFAULT VALUE
EC Enable
Enable/Disable
Global
EC Adapt Enable
Enable/Disable
Enable
EC NLP Enable
Enable/Disable
Enable
EC CNG Enable
Enable/Disable
Enable
ALC Enable
Enable/Disable
Global
Noise Reduction Enable
Enable/Disable
Global

Table: 6 lists the features that be controlled during an active call.

PARAMETER
VALID RANGE
Convergence Status
0..32767
G.165 Tone Detector Status
Null, G.164 Active, G.165 Active

Table: 7 lists the status parameters that are available during an active call.

VQE-168 ANSI “C” API

Control of the VQE-168 is facilitated by using an ANSI “C” set of API functions that are provided to run on the host processor. These functions configure and control the VQE-168 as well as return status information to the host application.

FUNCTION

VQE168Configure( .. )

VQE168SetupChannel( … )

VQE168TeardownChannel( … )

VQE168ControlChannel( … )

VQE168GetChannelStatus( … )

 

 

Adaptive Digital Technologies, Inc.
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