Progressive diversity allocation for progressive transmission of spiht packets in erasure channels

The SPIHT (set partitioning in hierarchical trees) algorithm, which works with the aid of the discrete wavelet transform (DWT), is one of the most renowned techniques for image compression. One problem with SPIHT image coding, especially when image transmission is involved, is that even just as few as one error in the embedded code sequence can render the decoded image completely unrecognizable. In this paper, we propose a scheme in which an SPIHT code sequence is packetized into two types: CP (critical packet) and RP (refinement packet). Then, we address the transmission of those SPIHT packets over erasure channels. The basic idea is to provide unequal error protection (UEP) to those packets by diversity (i.e., repeated transmissions) so that, at the receiver, the decoded image quality (measured in the expected SNR, signal-to-noise-ratio) is as good as possible. A diversity allocation (DA) algorithm, referred to as progressive diversity allocation (PDA), is proposed. It works in a fashion and is naturally compatible with the progressive transmission of SPIHT-encoded images. Experiments show that the PDA scheme produces good results, nearly as good as achieved by the method of full search.