Reducing the out-of-band radiation of OFDM using an extended guard interval

We investigate the spectrum, out-of-band radiation (OBR) and the use of extended guard interval (EGI) to reduce the out-of-band radiation of an OFDM signal when passing through different nonlinear devices. Spectra of the OFDM signal with different EGI lengths after passing through nonlinear devices are obtained through computer simulations. Mathematical expressions for the power spectral density of a conventional OFDM signal and an OFDM signal with different EGI lengths are also presented. Theoretical and simulated results are compared. Although the EGI reduces the OBR, this reduction is not significant in some cases. The effect of EGI on the OBR of an OFDM signal differs for different nonlinear devices. The EGI is also not capable of reducing the OBR caused by excessive clipping of the OFDM signal. Finally, it is also found that the length of the EGI does not have a considerable effect on the amount of OBR reduced when passing through a nonlinear devic

NOVEL OFDM SYSTEM BASED ON DUAL-TREE COMPLEX WAVELET TRANSFORM

The demand for higher and higher capacity in wireless networks, such as cellular, mobile and local area network etc, is driving the development of new signaling techniques with improved spectral and power efficiencies. At all stages of a transceiver, from the bandwidth efficiency of the modulation schemes through highly nonlinear power amplifier of the transmitters to the channel sharing between different users, the problems relating to power usage and spectrum are aplenty. In the coming future, orthogonal frequency division multiplexing (OFDM) technology promises to be a ready solution to achieving the high data capacity and better spectral efficiency in wireless communication systems by virtue of its well-known and desirable characteristics. Towards these ends, this dissertation investigates a novel OFDM system based on dual-tree complex wavelet transform (D