Introduction

Digital Voice System’s AMBE-2000™ Vocoder Chip is an extremely flexible, high-performance voice compression solution that provides exceptional voice quality at rates as low as 2.0 kbps and toll-quality at 4.0 kbps. The AMBE-2000™ Vocoder Chip is a low cost, DSP-based voice codec for full or half-duplex real and non-real time voice compression applications.

The AMBE-2000™ Vocoder Chip implements DVSI’s patented and award winning AMBE® Voice Compression Algorithm. The field-proven success of this technology has resulted in its recognition as the standard for voice quality in communication systems around the globe. Satellite systems such as ACeS, AMSC/TMI, ICO, Inmarsat, Iridium,  Optus and Thuraya use this technology because of its superior voice quality at low bit rates.

DVSI has packaged this advanced vocoder technology onto a proprietary chip from the world’s leading DSP manufacturer. This single-chip solution achieves a level of performance and reliability typically associated only with customized ASICs but without the risks and high-development costs.

DVSI developed the AMBE-2000™ Vocoder Chip to offer the latest AMBE® Voice Compression Technology with no licensing fees, royalties or the engineering expense typically associated with custom DSP software implementation. With small quantity off-the-shelf availability, this DSP provides low-risk cost-effective voice compression.

The AMBE-2000™ Vocoder Chip supports bit rates from 2000 to 9600 bps, formed from the combination of compressed speech data and Forward Error Correction (FEC) data . The AMBE-2000™ can change speech and/or FEC rates within one frame for on-the-fly flexibility.

Operation

With variable-rate high-performance FEC built-in, the AMBE-2000™ Vocoder Chip provides exceptional robustness to background noise and bit errors. Offering block and convolution codes with up to four bits of soft-decision decoding, the AMBE-2000™ Vocoder Chip can achieve peak performance in degraded channel conditions that include significant bit errors. The Viterbi decoder offers rates as low as R=1/4 for intelligible speech at up to 20% BER. This level of performance can lead to the successful development and deployment of wireless communication systems in the most demanding environments.

The AMBE-2000™ Vocoder Chip also includes a number of advanced features such as automatic Voice/Silence detection (VAD), adaptive comfort noise generation, DTMF and North American call progress tone detection and signaling, 16 ms echo cancellation and low-power consumption.

The AMBE-2000™ Vocoder Chip is easily configured to transmit and receive digitized speech to and from most linear, a-law, or u-law A/D-D/A codecs through its serial interface. The digitized speech from the external A/D is converted into compressed digital data (encoded) by the AMBE-2000™ Vocoder Chip and output to the channel interface.

The serial channel interface may use a processor, controller, modem or similar device to handle the transmission of the compressed voice data across a channel. Simultaneously, the AMBE-2000™ Vocoder Chip receives data from the other side of the channel. This data is (decoded) by the AMBE-2000™ Vocoder Chip, then reconstructed into a digital speech signal and sent to the D/A. The encoder and decoder functions are fully asynchronous for maximum flexibility.

Block Diagram
Click for Enlarged Block Diagram

The AMBE-2000™ Vocoder Chip employs DVSI’s latest AMBE-2000™ voice coder technology providing toll-quality speech at rates as low as 4.0 kbps. Along with improved performance and enhancements such as convolutional FEC coding, an operational mode exists that provides a seamless migration path into systems already using DVSI’s AMBE-1000™ Vocoder Chip.

The AMBE-2000™ Vocoder Chip offers the affordability, mobility and power efficiency required by virtually all personal communication devices. The chip is designed to be fully inter-operable with DVSI’s MultiMux™ Vocoder Board which provides sixteen full-duplex channels of voice compression. The integration of these two devices creates a complete system for an endless array of computer telephony and wireless communication applications.

The value of DVSI’s AMBE® Voice Compression Technology goes beyond low-bit-rate and voice quality. It has been thoroughly evaluated and tested by international manufacturers under various conditions using a variety of languages. This assures the user is getting the best vocoder available and makes the DVSI vocoder the logical choice without the need for additional comparison tests. Plus the fact, that DVSI’s Voice Compression technology has been implemented worldwide for more than ten years delivers the added security of a field proven technology that can play a key role in making any communication system an overall success.

Features

• AMBE+™ Vocoder - Toll-Quality at 4.0 kbps
  User selectable bit rate (2.0 kbps - 9.6 kbps)

• Integrated convolutional and block code
  Forward Error Correction (FEC)

• Viterbi Decoder (1/4 < rate < 1) with up to 4 bits
  of soft-decision decoding

• High-performance Voice Activity Detection (VAD)
  with adaptive Comfort Noise Insertion (CNI)

• Low Delay

• Echo Cancellation

Benefits

• Low Cost
  - Ideal for wireless products
  - No licensing fees or royalties
  - Low power consumption (65 mw @ 3.3v)
  - Single IC solution (100 pin TQFP)

• Simple Integration
  - Flexible A/D-D/A interface that works with many
     low cost codecs
  - User selectable speech and FEC rates for flexibility
     in system design
  - Serial channel interface with independent
     encoder and decoder rates
  - Interoperable with DVSI's AMBE-1000™ Vocoder Chip