tailieunhanh - Real-Time Digital Signal Processing - Chapter 9: Practical DSP Applications in Communications

There are many DSP applications that are used in our daily lives, some of which have been introduced in previous chapters. DSP algorithms, such as random number generation, tone generation and detection, echo cancellation, channel equalization, noise reduction, speech and image coding, and many others can be found in a variety of communication systems. In this chapter, we will introduce some selected DSP applications in communications that played an important role in the realization of the systems. . | Real-Time Digital Signal Processing. Sen M Kuo Bob H Lee Copyright 2001 John Wiley Sons Ltd ISBNs 0-470-84137-0 Hardback 0-470-84534-1 Electronic 9 Practical DSP Applications in Communications There are many DSP applications that are used in our daily lives some of which have been introduced in previous chapters. DSP algorithms such as random number generation tone generation and detection echo cancellation channel equalization noise reduction speech and image coding and many others can be found in a variety of communication systems. In this chapter we will introduce some selected DSP applications in communications that played an important role in the realization of the systems. Sinewave Generators and Applications When designing algorithms for a sinewave sine or cosine function generation several characteristics should be considered. These issues include total harmonic distortion frequency and phase control memory usage execution time and accuracy. The total harmonic distortion THD determines the purity of a sinewave and is defined as spurious harmonic power THD . . ----z--------- total wavelorm power where the spurious harmonic power relates to the unwanted harmonic components of the waveform. For example a sinewave generator with a THD of percent has a distortion power level approximately 30 dB below the fundamental component. This is the most important characteristic from the standpoint of performance. The other characteristics are closely related to details of the implementation. Polynomials can be used to express or approximate some trigonometric functions. However the sine or cosine function cannot be expressed as a finite number of additions and multiplications. We must depend on approximation. Because polynomial approximations can be computed with multiplications and additions they are ready to be implemented on DSP devices. For example the sine function can be approximated by . The implementation of a sinewave generation using .