| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 91 === In recent years, multicarrier systems have been chosen for many wireless and wired-line communicationsystems. Multicarrier systems usually use the Inverse Discrete Fourier Transform (IDFT) for modulation and Discrete Fourier Transform (DFT) for demodulation. When applied into a wireless environment, such as wireless LAN, Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), it is referred to as Orthogonal Frequency Division Multiplexing (OFDM). When applied into a wired-line environment, such as Asymmetric Digital Subscriber Line (ADSL), Very high speed Digital Subscriber Line (VDSL), it is referred to as Discrete Multitone (DMT) system.
Because the bandwidth of ADSL systems is over 130kHz-1104kHz, it suffers from the narrowband interferences, for example, a nearby AM radio station (530kHz-1600kHz). It is well known that DFT filters have a poor frequency attenuation and large spectral overlapping between adjacent subbands. The performance of DFT transceivers will degrade significantly in the presence of narrowband interferences.
In this thesis, we propose Windowed DMT (WDMT) to combat the
narrowband interferences. This scheme will not change the transmitter but involves the receiver design only. We also investigate the eigenfilter design for receiver. Finally, we simulate in DSL channel and RFI model, the results show that WDMT has a significant improvement in bit error rate (BER) and bit rate.
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