Pilot reuse sequences for TDD in downlink multi-cells to improve data rates

The exponential growth in demand for high data rate transmission to users in fifth generation wireless networks, focus there has been a particular research focus on new techniques that achievable high data rate by suppressing interference between neighboring cells. In this paper, we propose that system performance can be improved by using perfect channel estimation and reducing effective interference with pilot reuse that mitigate strong pilot contamination based on the knowledge of large-scale fading coefficients. We derived the lower bounds on the achievable data rate in downlink by analyzing the performance of the zero-forcing precoding method and derive the signal-to-interference noise ratio to mitigate interference between neighboring cells. From the simulation results, the large pilot reuse sequences improved the achievable data rate and provided better estimation for a channel. When the number of users is large, the interference between neighboring cells can be suppressed by using orthogonal pilot reuse sequences

Bat algorithm–based beamforming for mmWave massive MIMO systems

© 2019 John Wiley & Sons, Ltd. In this paper, an optimized analog beamforming scheme for millimeter-wave (mmWave) massive MIMO system is presented. This scheme aims to achieve the near-optimal performance.by searching for the optimized combination of analog precoder and combiner. In order to compensate for the occurrence of attenuation in the magnitude of mmWave signals, the codebook-dependent analog beamforming in conjunction with precoding at transmitting end and combining signals at the receiving end is utilized. Nonetheless, the existing and traditional beamforming schemes involve a more difficult and complicated search for the optimal combination of analog precoder/combiner matrices from predefined codebooks. To solve this problem, we have referred to a modified bat algorithm to find the optimal combination value. This algorithm will explore the possible pairs of analog precoder/combiner as a way to come up with the best match in order to attain near-optimal performance. The analysis shows that the optimized beamforming scheme presented in this paper can improve the performance that is very close to the beam steering benchmark that we have considered.Published versio