The Design Of Transcendental Functions Based On The DSP For Wireless Communication

Wireless communication is the exchange of information communication mode viathe propagation of electromagnetic signal in free space. Recently, the in-depth researchand development in wireless mobile communication system required high performanceof the processor in the driving device. Digital signal processor (DSP), which hashigh-speed, high integration, low power, parallel structure, and improved developmentenvironment, simulation module and debugging interface, is precisely needed in thenew wireless communication. Thus, the technology that wireless communicationcombined with the DSP chip has obtained more widely application. The Tricorestudied in this paper integrates DSP and MCU into a RISC-based32-bit CPU core.In mathematics, transcendental functions refer to the relationship betweenvariables cannot be get from limited times of addition, subtraction, multiplication,division, involution, evolution, in contrast with algebraic functions. For example,exponential, logarithmic, trigonometric and inverse trigonometric functions belong totranscendental functions and elementary transcendental functions. What we studied isthe exponential and logarithmic functions in elementary transcendental functions.Exponentiation and logarithms are inevitable in MAP algorithm and Log-MAPalgorithm of turbo code. Experiments show that the complexity of exponential,logarithmic directly affects the efficiency of the algorithm greatly. Existing researchavoid exponentiation and logarithms arithmetic by changing the algorithm or functionapproximation, so as to simplify the computational complexity.In order to solvenumbers of exponential and logarithmic arithmetic in the MAP and Log-MAPalgorithm, the instruction used for exponential and logarithmic arithmetic wasextended based on the original instructions of Tricore circuit in this paper. Itsinstruction could be called by MAP and Log-MAP algorithm to reduce the arithmeticcomplexity, since its function was achieved in the circuit.First, we studied the algorithm theory of exponential and logarithmic, includingfull look-up table method, extended look-up table method, Taylor expansion method,linear approximations method and look-up table combined with the linearapproximation method, and compared the accuracy and storage space of variousalgorithms. Second, the specialized extend instruction designed for exponential andlogarithmic arithmetic was proposed in the paper based on the structure of Tricore circuit and the format of instruction set. Third, the basic system architecture of thecoprocessor kernel was realized by Verilog HDL, and an optimization method, whichwill add a flag signal, is proposed to increase the accuracy of the coprocessor. Finally,the function simulation and verification of the various algorithm such as exponentialand logarithmic and the designed the coprocessor were completed.