Widely-linear precoders and decoders for MIMO channels

This paper deals with the problem of jointly designing optimum widely-linear (WL) precoders and decoders for multiple-input multiple-output (MIMO) channels, by adopting as a specific design target the minimization of the symbol mean square error and assuming that channel state information is available at both the transmitter and receiver sides. In the proposed scheme, vectors of symbols are precoded through a WL mapping, which jointly operates on the symbol block and its complex-conjugate version; additionally, a WL receiver processes both the received signal and its complex-conjugate counterpart. By using a complex-valued representation of the relevant vectors involved in the design of the WL-MIMO transceiver, we show how the optimization framework originally developed for linear precoding/decoding MIMO structures can be extended to the case where the transmitted symbols and/or the disturbance exhibit improper or noncircularity features

Performance analysis of FBMC over OFDM in Cognitive Radio Network

Cognitive Radio (CR) system is an adaptive, reconfigurable communication system that can intuitively adjust its parameters to meet users or network demands. The major objective of CR is to provide a platform for the Secondary User (SU) to fully utilize the available spectrum resource by sensing the existence of spectrum holes without causing interference to the Primary User (PU). However, PU detection has been one of the main challenges in CR technology. In comparison to traditional wireless communication systems, due to the Cross-Channel Interference (CCI) from the adjacent channels used by SU to PU, CR system now poses new challenges to Resource Allocation (RA) problems. Past efforts have been focussed on Orthogonal Frequency Division Multiplexing (OFDM) based CR systems. However, OFDM technique show various limitations in CR application due to its enormous spectrum leakage. Filter Bank based Multicarrier (FBMC) has been proposed as a promising Multicarrier Modulation (MCM) candidate that has numerous advantages over OFDM. In this dissertation, a critical analysis of the performance of FBMC over OFDM was studied, and CR system was used as the testing platform. Firstly, the problem of spectrum sensing of OFDM based CR systems in contrast to FBMC based were surveyed from literature point of view, then the performance of the two schemes was analysed and compared from the spectral efficiency point of view. A resource allocation algorithm was proposed where much attention was focused on interference and power constraint. The proposed algorithms have been verified using MATLAB simulations, however, numerical results show that FBMC can attain higher spectrum efficiency and attractive benefit in terms of spectrum sensing as opposed to OFDM. The contributions of this dissertation have heightened the interest in more research and findings on how FBMC can be improved for future application CR systems