Performance evaluation of hybrid millimeter wave systems under limited information

Abstract

Sem resumo disponível.

The increase of electronic devices with wireless connections, end up presenting problems to the current architectures. The current 4G architecture can not handle the demands that arise from the increase of users and it will be necessary to deal with higher tra c and connections with higher transmission rate. Consequently, to meet these requirements, new technologies and techniques are needed for the next generation(5G). Techniques such as the use of millimeter waves, combined with terminals equipped with large antenna arrays or massive number of antennas, although promising and presenting good results, bring with them new problems. Millimeter waves due to the smaller wavelength will allow systems with massive number of antennas. New transmit and receive signal processing (e.g. hybrid beamforming) has been proposed for millimeter wave communications combined with a massive number of antennas. However, transmit beamforming requires the knowledge of channel state information prior to the transmission. Therefore the design of e cient feedback techniques is of paramount importance for pratical systems. This issue is more relevant for massive MIMO based systems than for the conventional MIMO systems. For the rst one the channel information to fed back is much higher. In this dissertation a low-overhead feedback channel quantization scheme is proposed. Then, a single-user mmW massive MIMO system is evaluated under the developed quantization strategy. It was considered a transmitter employing a hybrid analog-digital equalizer. The considered techniques quantizes separately some channel parameters, such as complex fading amplitudes, transmit and receive array response. After that, these quantized parameters are fed back to the transmitter and the channel is reconstructed in order to compute the transmit beamformers. The results have shown that a very low number of bits is needed to obtain a performance close to the one obtained with perfect channel information.