10,336 research outputs found
Millimeter Wave Communications with Reconfigurable Antennas
The highly sparse nature of propagation channels and the restricted use of
radio frequency (RF) chains at transceivers limit the performance of millimeter
wave (mmWave) multiple-input multiple-output (MIMO) systems. Introducing
reconfigurable antennas to mmWave can offer an additional degree of freedom on
designing mmWave MIMO systems. This paper provides a theoretical framework for
studying the mmWave MIMO with reconfigurable antennas. We present an
architecture of reconfigurable mmWave MIMO with beamspace hybrid analog-digital
beamformers and reconfigurable antennas at both the transmitter and the
receiver. We show that employing reconfigurable antennas can provide throughput
gain for the mmWave MIMO. We derive the expression for the average throughput
gain of using reconfigurable antennas, and further simplify the expression by
considering the case of large number of reconfiguration states. In addition, we
propose a low-complexity algorithm for the reconfiguration state and beam
selection, which achieves nearly the same throughput performance as the optimal
selection of reconfiguration state and beams by exhaustive search.Comment: presented at IEEE ICC 201
Codebook Based Hybrid Precoding for Millimeter Wave Multiuser Systems
In millimeter wave (mmWave) systems, antenna architecture limitations make it
difficult to apply conventional fully digital precoding techniques but call for
low cost analog radio-frequency (RF) and digital baseband hybrid precoding
methods. This paper investigates joint RF-baseband hybrid precoding for the
downlink of multiuser multi-antenna mmWave systems with a limited number of RF
chains. Two performance measures, maximizing the spectral efficiency and the
energy efficiency of the system, are considered. We propose a codebook based RF
precoding design and obtain the channel state information via a beam sweep
procedure. Via the codebook based design, the original system is transformed
into a virtual multiuser downlink system with the RF chain constraint.
Consequently, we are able to simplify the complicated hybrid precoding
optimization problems to joint codeword selection and precoder design (JWSPD)
problems. Then, we propose efficient methods to address the JWSPD problems and
jointly optimize the RF and baseband precoders under the two performance
measures. Finally, extensive numerical results are provided to validate the
effectiveness of the proposed hybrid precoders.Comment: 35 pages, 9 figures, to appear in Trans. on Signal Process, 201
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