Development of Audio Codec for Mobile System WCDMA

Abstract

The Wide-Band Code Division Multiple Access is the technology of the third generation mobile systems. It has many advantages over the second generation mobile systems. It has better bandwidth efficiency. In addition, wide-band services such as videophone and Internet services are provided including video streaming. Recently new digital audio applications have been used for network, broadcasting and multimedia which face constraints such as channel bandwidth. The audio of CD quality using sampling frequency 44.1 KHZ, 16 bits, 2 channels requires 1.411.200 bits per second that means to be able to play an audio file with CD quality, we need more than 1.4 Mbit/s in band width. So different compression methods have been used to decrease bandwidth and keep the same quality of audio signal. The international standard ISO 11172-3 defines three different methods of increasing complexity and compression efficiency for perceptual coding of audio signal. This thesis deals exclusively with the third method also known as MP3. It has become very popular for compressing CD quality music with almost no audible degradation. MP3 depends on psychoacoustic model which used in encoder only to decide which parts of the signal are irrelevant and which parts are not, and remove the inaudible parts. In chapter 1, introduction to WCDMA system has been mentioned and different audio formats have been discussed.