由於多媒體技術的迅速發展，使用者對多媒體的需求量大增，其中又以影像傳輸所需的資料量最大，故在有限的記憶體儲存容量中，有效的壓縮及傳輸方法是迫切需要的。
其中離散小波轉換技術之特點非常適合使用於影像壓縮，而基於離散小波轉換技術下所發展的SPIHT壓縮方法亦有許多優點，不僅能在無雜訊干擾的情況下壓縮出高品質的影像，
且編解碼效率高，亦能提供漸進式傳輸。不過SPIHT壓縮在影像傳輸上卻有一致命缺點，即是其編碼後的位元序列對雜訊極為敏感，即使只是一個位元的錯誤也有可能造成不可補救的錯誤。

在本論文中，我們研究了SPIHT編碼的位元序列特性，並依其特性將此缺點進一步改善，使其在通道中能有效對抗雜訊且順利被傳送至接收端。我們假設通訊場景為無回傳機制，
因此在錯誤保護機制中我們亦同時使用了里德-所羅門碼。在所提出的傳輸機制中，經由我們所提出的最佳打包機制將訊息打包成各種具有不同更正參數且封包長度都固定的封包，
並利用SPIHT的編解碼特性使用漸進式多樣性分配給予封包不同重要性的分配，達到不等錯誤保護，使能保證接收端受到最佳品質的影像。我們以模擬來驗證此系統的效能，
並與其他兩種機制作為比較，其中一種亦為封包附有可選擇性里德-所羅門碼，而另一種則為不可選擇性里德-所羅門碼。實驗結果證實在通道訊雜比很低時，我們所提出的機制明顯優於以往的打包方式。

As a result of the rapid development of multimedia technologies, effective compression and transmission methods under limited resources (storage and bandwidth)
are needed. The characteristics of the wavelet transforms make it suitable for image compression. Coupled with the discrete wavelet transform (DWT),
set partitioning in hierarchical trees (SPIHT) is a highly efficient image compression technique that allows for progressive transmission.
One issue with SPIHT, however, is that its decoding can be extremely sensitive to errors in the embedded bit stream generated by the encoder.

In this thesis, we address the issue of transmitting SPIHT-encoded images via noisy channels, wherein errors are inevitably
encountered. The communication scenario assumed in this thesis is that no acknowledge path is available from the receiver to
the transmitter. Therefore, the error protection is done in the forward fashion (i.e. by forward error correction). More
specifically speaking, the error protection is implemented with the combination of Reed-Solomon codes and the technique of diversity.

In the proposed scheme, the SPIHT data sequence is divided into packets (referred to as source packets). In the mean time,
we have a code selection mechanism to select, among four different code rates, a Reed-Solomon code for each source packet.
The resulted packet is called a channel packet. To fight the Rayleigh fading encountered in the channel, each channel packet
is repeatedly transmitted for a "diversity-order" of times. The combination of diversity and Reed-Solomon codes provide unequal
error protection (UEP) to the source packets. The determination of the diversity order for each packet is the main task of this work.
We propose a scheme called "progressive diversity allocation" (PDA) to do this. Its computation complexity is very low, and it produces very good decoded image quality.
Moreover, it is observed that the incorporation of several code rates, instead of just a fixed code rate, improves the decoded images, especially when the channel signal-to-noise ratio (SNR) is low.

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