A Transcoding-Free Multiple Description Coder for Voice over Mobile Ad-Hoc Networks

We propose a new multiple description (MD) coder design based on the Adaptive Multi-Rate Wideband (AMR- WB) coder that can support transcoding-free communication between an ad-hoc network and another network that supports the AMR-WB codec. The encoder of the MD coder consists of the standard AMR-WB coder and a bit-stream splitting block that splits the AMR-WB bit-stream into two balanced descriptions. The decoder consists of a bit-stream substitution block that substitutes the missing bits, when only one description is received, to construct a valid AMR-WB frame that can be decoded using the standard AMR-WB decoder. We show that the performance of the new MD coder is better than a previous non-transcoding- free MD coder based on AMR-WB when transcoding is required and it is significantly better than using a single description of AMR-WB over the ad-hoc network supporting transcoding-free communication.