On the Improvement of the Achievable bit rate in Multicarrier Communication Systems Using Signal Processing Techniques

Abstract

<p>With the growing demand for high data rate communication services, multi-carrier communication schemes have started to become the method of choice in many applications. In this thesis, multi-carrier communication systems are studied and various methods for improving their achievable bit rate arc proposed.</p> <p>Filtered multitone (FMT) is a multi-carrier communication scheme which is implemented using a modulated filter bank structure. In this thesis, an efficient design method for the prototype filter of the FMT system is proposed. This design method allows improvement of the achievable hit rate by efficient evaluation of the inherent trade-off between the sub channel spectral containment provided by the prototype filter and the intersymbol interference (lSI) that the filter generates. Numerical results further demonstrat.e the effectiveness of the proposed design method. The insight gained from this design is also used to determine the optimal number of subchannels in FMT systems. Moreover, since the presence of lSI in FMT subchannels outputs renders the conventional water-filling power loading algorithm suboptimal, we propose an efficient power loading algorithm for Fl\IT that enables higher achievable bit rates.</p> <p>Discrete multitone (DMT) is a popular multi-carrier communication scheme, mainly due to its rather low complexity. However. DMT suffers from poor subchannel spectral characteristics. In this thesis, a family of bi-windowed DMT transceivers is proposed that provide both improved sub channel 8pectral containment at the transmitter and improved spectral selectivity at the receiver, without requiring the cyclic prefix to be longer than the order of the channel impulse respon8e. The window8 arc designed in a channel independent manner and are con8trained to produce sub channel outputs that arc free from lSI. Furthermore, the design allows the interisubchannel interference (leI) to be controlled in such a way that it can be mitigated using a relatively simple minimum mean square error (MMSE) successive interference cancellation scheme. Numerical results demonstrate the significant gain in the achievable bit rate obtained Ly the proposed scheme.</p>