Proposal of Wireless Communication

Simulation of Suppression of Frequency Selective Fading by OFDM Based on Matlab

Yunjun Zheng, 14010410023

Email: [e-mail]

 

    In the wireless communication, the signal is multipath. When the bandwidth of the signal is much larger than the coherent bandwidth of the channel,frequency selective fading will occur. If linear modulation is used, the signal will have significant intersymbol interference in the time domain^[1]. In order to overcome this problem, multicarrier modulation can be used. The basic idea is to divide the channel into multiple subchannels so that the bandwidth of each subchannel is less than the coherent bandwidth of the original channel, so that the fading of each subchannel can be approximated as a flat fading rather than frequency selective fading; At the same time, the high-speed transmission bit stream should be divided into a low-rate data stream by serial-to-parallel conversion^[2], and then different subcarriers are used for modulation and then the multiplexed modulated signals are superimposed together to form a transmission signal. Orthogonal frequency division multiplexing (OFDM)is such a multi-carrier modulation technology. In addition, the spectrum of its subcarriers is half overlapping but keeps orthogonal to each other^[2], so OFDM is an efficient modulation technique.

    This project will use Matlab to simulate the suppression of frequency selective fading by OFDM, including the following parts:

    ① Channel modeling: To establish a channel model with frequency selective fading characteristic, to obtain the unit impulse response or transfer function of the channel;

    ② Signal generation: To calculate the coherence bandwidth of the channel, to determine the number of sub-channels and sub-carriers, to generate sub-carrier signals, the serial and serial conversion of the original digital signal;

    ③ Modulation and demodulation: Mainly include signal and carrier multiplication, IFFT, parallel and serial conversion, serial and parallel conversion, FFT, parallel and serial conversion;

    ④ Performance analysis: To calculate the error rate of the received signal, to compare the linear single carrier modulation system with OFDM system;

    ⑤ Visual output of simulation results: Mainly use pictures and forms.

 

References

[1] Andrea Goldsmith. Wireless Communication[M]. New York: Cambridge University Press, 2005.

[2] Hui Zhang, Lina Cao. Modern Communication Principles and Techniques (3rd Edition)[M]. Xi’an: Press of Xidian University, 2013.

张辉, 曹丽娜. 现代通信原理与技术（第三版）[M]. 西安: 西安电子科技大学出版社, 2013.