15 research outputs found
NOMA Meets Finite Resolution Analog Beamforming in Massive MIMO and Millimeter-Wave Networks
Finite resolution analog beamforming (FRAB) has been recognized as an
effective approach to reduce hardware costs in massive multiple-input
multiple-output (MIMO) and millimeter-wave networks. However, the use of FRAB
means that the beamformers are not perfectly aligned with the users' channels
and multiple users may be assigned similar or even identifical beamformers.
This letter shows how non-orthogonal multiple access (NOMA) can be used to
exploit this feature of FRAB, where a single FRAB based beamformer is shared by
multiple users. Both analytical and simulation results are provided to
demonstrate the excellent performance achieved by this new NOMA transmission
scheme
Machine Learning Inspired Energy-Efficient Hybrid Precoding for MmWave Massive MIMO Systems
Hybrid precoding is a promising technique for mmWave massive MIMO systems, as
it can considerably reduce the number of required radio-frequency (RF) chains
without obvious performance loss. However, most of the existing hybrid
precoding schemes require a complicated phase shifter network, which still
involves high energy consumption. In this paper, we propose an energy-efficient
hybrid precoding architecture, where the analog part is realized by a small
number of switches and inverters instead of a large number of high-resolution
phase shifters. Our analysis proves that the performance gap between the
proposed hybrid precoding architecture and the traditional one is small and
keeps constant when the number of antennas goes to infinity. Then, inspired by
the cross-entropy (CE) optimization developed in machine learning, we propose
an adaptive CE (ACE)-based hybrid precoding scheme for this new architecture.
It aims to adaptively update the probability distributions of the elements in
hybrid precoder by minimizing the CE, which can generate a solution close to
the optimal one with a sufficiently high probability. Simulation results verify
that our scheme can achieve the near-optimal sum-rate performance and much
higher energy efficiency than traditional schemes.Comment: This paper has been accepted by IEEE ICC 2017. The simulation codes
are provided to reproduce the results in this paper at:
http://oa.ee.tsinghua.edu.cn/dailinglong/publications/publications.htm
Energy Efficiency and Asymptotic Performance Evaluation of Beamforming Structures in Doubly Massive MIMO mmWave Systems
Future cellular systems based on the use of millimeter waves will heavily
rely on the use of antenna arrays both at the transmitter and at the receiver.
For complexity reasons and energy consumption issues, fully digital precoding
and postcoding structures may turn out to be unfeasible, and thus suboptimal
structures, making use of simplified hardware and a limited number of RF
chains, have been investigated. This paper considers and makes a comparative
assessment, both from a spectral efficiency and energy efficiency point of
view, of several suboptimal precoding and postcoding beamforming structures for
a cellular multiuser MIMO (MU-MIMO) system with large number of antennas.
Analytical formulas for the asymptotic achievable spectral efficiency and for
the global energy efficiency of several beamforming structures are derived in
the large number of antennas regime. Using the most recently available data for
the energy consumption of phase shifters and switches, we show that
fully-digital beamformers may actually achieve a larger energy efficiency than
lower-complexity solutions, as well as that low-complexity beam-steering purely
analog beamforming may in some cases represent a good performance-complexity
trade-off solution.Comment: Submitted to IEEE Transactions on Green Communications and Networkin
Low-complexity switching network design for hybrid precoding in mmWave MIMO systems
© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper deals with the design of a hybrid precoder for millimeter-wave MIMO systems. For the sake of concreteness, we consider an analog processing stage composed of a switching network with analog combining. The main contribution of this work consists on the proposal and evaluation of an optimization procedure based on a smart relaxation. The optimal hybrid precoder under a transmit power constraint is derived, after which, the analog precoding matrix is binarized. After an intuitive reasoning, we note that multiple solutions exist. Nevertheless, the (very) reduced computational complexity of the proposed optimization scheme makes it feasible for realistic implementations. Numerical results are reported to assess the performance of proposed hybrid precoder design.Peer ReviewedPostprint (published version