|
Recently, several methods that divide the original bitstream of an image/video progressive wavelet based source coders into multiple correlated substreams have been proposed. The principle behind transmitting independent multiple substream is to generate multiple descriptions of the source such that the graceful degradation is
achieved when transmitted over severe fading channels and lossy packet networks since some of the streams may be recovered. Noting that multiple substream can benefit from multiple independent channel paths, we naturally consider Multi-Input Multi-Output communication systems where we obtain multiple independent fading channels. Depending on several factors including: the number of antennas employed, the transmission energy, the Doppler shift (due to the motion between the transmitter antenna and receiver antennas), the
total transmission rate and the distortion-rate (D-R) of the source-there exists an optimal number of balanced substreams and an optimal joint source-channel coding policy such that the expected distortion at the receiver is minimized. In this paper we derive an expected distortion function at the receiver based on all of these parameters and provide a fast real-time numerical technique to find the optimal or near optimal number of balanced substreams to be transmitted. This expected distortion is based on our derivation of the probabilistic loss patterns of a balanced multiple substream progressive source coder. The accuracy of the derived expected distortion estimator is confirmed by Monte-Carlo simulation employing Dent's modification of Jakes' model. By accurately estimating the optimal number of balanced substreams to be transmitted, a substantial gain in visual quality at low and intermediate signal-to-noise ratio (SNR) is obtained over severely fading channels. At high SNR, the single stream source coder's source efficiency makes it slightly better than the multiple substream source coder. Overall, using our analytic development, we provide a systematic real-time non-adhoc method that achieves high quality image and video at low and moderate signal-to-noise ratios in severe fading channels for single and multiple antenna systems.
|
