The Performance Comparison Of SC/FDE And OFDM

With people's increasing requirements for all kinds of real-time multimedia service and the rapid development of the Internet, broadband wireless communication has become a full potential in the development of wireless communication. In the system of wireless broad band communication, the multi-path effect may greatly affect the reliability of the communication performance. Therefore, how to enhance the transportation performance of the system is closely related to the scheme adopted for countermining the channel multi-path effect. OFDM (Orthogonal Frequency Division Multiplexing) and SC-FDE (Single Carrier Transmission with Frequency Domain Equalization) was proposed to be the key technologies in IEEE802.16a. standard. Meanwhile, these two schemes belong to the key technologies of the forth generation mobile communication. The research work to these schemes is very important for the development of wireless communication.Firstly, the characteristics of radio channels are introduced and the model of impulse response in time-variant and multi-path channels is described. Furthermore, channel estimation and equalization technology is explained to overcome the channel fading.OFDM is a multiple carrier digital modulation technology based on the DFT(Discrete Fourier Transform). This thesis explained the principle of OFDM detailedly. According to the description for the OFDM technology in IEEE 802.16a, a physical layer simulation model is established. The result proves that OFDM is a effective way to overcome the multi-path effect. However, OFDM technology also has some defects in nature, such as the high complexness of computation, high sensitivity to the offset of carrier frequency and the phase noise. These characteristics brought a higher demand for the hardware.SC-FDE is a more effective way to overcome the multi-path effect of the wireless broad band transport system. It combines the strength of OFDM and SC-FDE and counterbalance the deficiency of OFDM technology. SC-FDE has become a competitive scheme for future high rate wireless communication system. This thesis explained the technology principle and various of equalization methods in SC-FDE. A simulation model is also established.Finally, we compare the BER (bit error rate) of the two schemes in a same simulation condition. The research result indicates that the BER of OFDM is lower than SC/FDE in a communication system having a low SNR (signal to noise ratio). When the SNR is high in a communication system, the BER of SC/FDE is obviously higher than OFDM. This conclusion is of reference value in applying the technology of SC-FDE and OFDM to an actual communication system.