A 4 N-QAM ADAPTIVE DECISION DEVICE TO MITIGATE I/Q IMBALANCE AND IMPAIRMENTS CAUSED BY TIME-VARYING FLAT FADING CHANNELS

Abstract. In this work, we propose an adaptive decision device based on a Kohonen network that can automatically generate the classes associated with each symbol of a 4 n-QAM in the presence of nonlinearities caused by the I/Q imbalance and additive Gaussian white noise, being also capable of compensating phase and gain variations produced by a time-varying flat-fading channel. Our proposal can achieve optimality in the maximum-likelihood sense with a small computational cost. Furthermore, due to the tracking ability inherent to the devised scheme, there is no need for an automatic gain controller or a phase-locked loop

Design,Simulation and Hardware Implementation of a Digital Television System: Synchronization Techniques (Invited Paper)

supported many research consortia in order to develop a Digital Television System employing advanced technologies for multimedia broadcasting. One of the proposals for the physical layer of this system was entitled Innovative Modulation for the Brazilian Digital TV System (MI-SBTVD). The MI-SBTVD Project includes high performance error-correcting codes, transmit spatial diversity and multi-carrier modulation. The objective of this article is to present the synchronization techniques that were used in the first proof-of-concept for the MI-SBTVD System. We present the simulated performance results for both the AWGN and multipath channels. Finally, we also comment on the implementation details of the synchronization scheme using Field Programmable Gate Array (FPGA) devices

Immune-inspired Dynamic Optimization for Blind Spatial Equalization in Undermodeled Channels

Abstract—In this work, we propose an evolutionary-like approach to the problem of blind adaptive spatial filtering that is based on the decision-directed criterion and on the doptaiNet, an artificial immune network conceived to perform multimodal search in dynamic environments. The proposal was tested under static and time-varying undermodeled channel models, and, in all cases, its ability to find and track a solution close to the Wiener global optimum was attested. The obtained results reveal that the dopt-aiNet may decisively enhance the performance of adaptive arrays in scenarios built from elements that are representative of some aspects of real-world communication systems