Look-ahead predictive trellis-coded quantization with nonlinear filters for image transmission over tactical channels

Many battlefield applications require the ability to transmit images over narrow bandwidth noisy channels. Previous research has demonstrated that the utilization of predictive trellis-coded quantization (PTCQ) incorporating a nonlinear prediction filter results in a method of robust source coding. Robust source coding provides both compression and noise mitigation without the need to allocate additional bandwidth for channel coding. However, the traditional PTCQ algorithm is suboptimal. This suboptimality arises from the prediction operation; a trellis path is eliminated in favor of the survivor path at each stage in time to form the input to the prediction filter. It is reasonable to assume that this eliminated path may have produced al lower overall distortion than the survivor path. In this paper we address this suboptimality by incorporating a look-ahead stage into PTCQ algorithm. This 'less-greedy' approach allows coding gains with a slight increase in overhead. The resulting algorithm yields an image encoding technique, which enables resilient image transmission over tactical channels.