Abstract
Orthogonal frequency division multiplexing (OFDM) is a strong candidate for the next generation wireless communica-tion. But the frequency offset between the local oscillators at the transmitter and receiver causes a single frequency offset in the signal, while a time-varying channel can cause a spread of frequency offsets known as the Doppler spread. Frequency offsets ruin the orthogonal of OFDM sub-carriers and cause inter-carrier interference (ICI), therefore, quickly diminishing the performance of the system. A novel all phase OFDM (AP-OFDM) system is established. APFFT is introduced for the first time to overcome ICI aroused by carrier frequency offset (CFO) in OFDM systems. This scheme makes use of APFFT in time domain and zero inserting in frequency domain to reduce the amount of ICI gener-ated as a result of frequency offset, with little additional computational complexity. At the same time, the proposed sys-tem has zero phase error. It is proved to be correct and effective in mathematics. The simulation results indicate that AP-OFDM system has a better performance than conventional OFDM system.
Highlights
Orthogonal frequency-division multiplexing (OFDM) communication systems require precise frequency synchronization [1,2,3,4], since otherwise inter-carrier interference (ICI) will occur
Its sensitivity to ICI caused by carrier frequency offset (CFO) is lower and APFFT is more suitable for Orthogonal frequency division multiplexing (OFDM) system
Compared with conventional OFDM system, APFFT reduce the sensitivity of system to CFO
Summary
Orthogonal frequency-division multiplexing (OFDM) communication systems require precise frequency synchronization [1,2,3,4], since otherwise inter-carrier interference (ICI) will occur. While many methods exist that can estimate and remove the frequency offset quite accurately, they often have considerable computational complexity Another approach is to use signal processing and/or coding to reduce the sensitivity of the OFDM system to the frequency offset [8]. These methods can either be used as low complexity alternatives to fine frequency-offset estimation techniques or they can be used together with a somewhat accurate oscillator. The advantages of APFFT are zero phase error and less ICI It improves the OFDM system's ability to resist frequency offset with the cost of limited additional computational complexity
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