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Hughes Network Systems

Vocoder Development

Brief

Hughes Network Systems LLC asked Cambridge Consultants to develop an ultra-low bit rate voice codec for use in the next generation Access Network Controller (ANC) for Iridium Satellite LLC. The ANC is a high availability system providing functionality similar to the Base Station Controller (BSC) in terrestrial mobile wireless networks.

Approach

To achieve the high density of codec channels required per DSP blade we used Texas Instruments’ high performance TMS 320C6474 DSP. Starting from a simple model of the voice codec we developed a fully re-entrant and highly robust codec implementation.

Our comprehensive audio verification environment was used to test a suite of factors such as voice quality, time stretching and error recovery and to ensure interoperability with terminal equipment.

Benefit

In an accelerated development programme of just 3 months we delivered a voice codec capable of scaling to 1000s of channels on DSP farm blades and meeting the stringent reliability requirements on the ANC.