The Design And Realization Of OFDM Baseband Modulaion And Demodulation System On DSP Technology

In recent years, Orthogonal Frequency Division Multiplexing (OFDM) has played an important part in wireless communication area, it support high data transfer rate which nearly reach the Nyquist limit in theory. It also has a strong resistance against multipath inter-symbol interference (ISI) and multipath fading. Besides, it has a useful feature that we can remove the conventional channel compensator in receiving device. Accompany with the continuous development and maturity of some OFDM's key technology, OFDM has been applied in digital audio broadcasting (DAB), digital television broadcasting (DVB), WLAN, WiMAX, and some other systems. In the mean time, most of all next generation wireless communication standards will use OFDM as their physical layer technology. In 802.16e (WiMAX) system, OFDM is also necessary, and OFDMA has been supported. This article will analysis and design a DSP platform based on the parameters of OFDM modulation and demodulation system in 802.16e standard.First, the article will analyze the basic principle of OFDM modulation and demodulation systems, introduce some associated channel coding and decoding method. Then it will select a helpful and simple method for DSP and some modules'realize, refer to the parameters of 802.16e standard. This system has a 256 point FFT length, and it will use RS block coding and convolutional coding for inner code. For the decoding technology, it will take the viterbi decoding method and Euclidean algorithm, it analysis each module'basic algorithm and realization method at the same time. At the end of this part, it will verify the feasibility and performance of some main module by using matlab tools.Second, the article designed a hardware platform to perform those algorithms, it can verify the algorithms'correctness and performance in actual hardware environment. In this part, will mainly analysis the connecting method between DSP's host interface (HPI) or multi-channel serial communication port (McBSP) and peripheral devices, it will also describe the connection between CY7C68013 USB interface and PC. In the end, I designed the power supply and reset module.The most important part of this system is software design. First this part will analyze the initialization of DSP and USB firmware design, this will ensure the PC DSP and D/A module work correctly. Then it will elaborate the software realization method of OFDM system. By flexible storage management this part of article will achieve continuous viterbi decoding and RS block decoding, and other demodulator module. In the end of this article, I will show the waveform of each module of DSP demodulator and verify the system's performance and correctness.