I. INTRODUCTION

Introduction to Error control coding :
     Error control coding (ECC), or channel coding, is a method of adding redundancy to information so that it can be transmitted over a noisy channel to another party, and subsequently be checked and corrected for errors that occurred in transmission. Channel coding is especially beneficial for wireless and multimedia applications, like phone communications and high television broadcasting. It is also favorable in deep space and satellite communications, and digital communication and storage. Figure 1.1 shows the basic layout of how information is transmitted and received in an error control coded channel.

     First, data is digitally recorded and compressed. Next, the data is encoded by error control coding. Following that, it is modulated from digital data to an analog signal and is amplified for transmission through the channel. On the receiving end, an analog signal is received and demodulated back to a digital signal. The data is then processed in the error control decoder, using the redundancy to correct the errors that occurred in transmission. Finally, the data is uncompressed and presented. The result is what you hear and see on your digital radio, digital TV, and computer. Some media types, as shown below in Table 1.1 [1], are very sensitive to errors. It is especially important to keep errors in these transmissions as low as possible.

Table 1.1 Sensitivity to Error
Media	Sensitivity to Error
Uncompressed Voice	Low Sensitivity
Uncompressed Video	Low Sensitivity
Compressed Voice	High Sensitivity
Compressed Video	High Sensitivity
Data	High Sensitivity

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