897 research outputs found
A High-Accuracy Adaptive Beam Training Algorithm for MmWave Communication
In millimeter wave communications, beam training is an effective way to
achieve beam alignment. Traditional beam training method allocates training
resources equally to each beam in the pre-designed beam training codebook. The
performance of this method is far from satisfactory, because different beams
have different beamforming gain, and thus some beams are relatively more
difficult to be distinguished from the optimal beam than the others. In this
paper, we pro- pose a new beam training algorithm which adaptively allocates
training resources to each beam. Specifically, the proposed algorithm allocates
more training symbols to the beams with relatively higher beamforming gain,
while uses less resources to distinguish the beams with relatively lower
beamforming gain. Through theoretical analysis and numerical simulations, we
show that in practical situations the proposed adaptive algorithm
asymptotically outperforms the traditional method in terms of beam training
accuracy. Moreover, simulations also show that this relative performance
behavior holds in non-asymptotic regime
Millimeter Wave MIMO Channel Estimation Based on Adaptive Compressed Sensing
Multiple-input multiple-output (MIMO) systems are well suited for
millimeter-wave (mmWave) wireless communications where large antenna arrays can
be integrated in small form factors due to tiny wavelengths, thereby providing
high array gains while supporting spatial multiplexing, beamforming, or antenna
diversity. It has been shown that mmWave channels exhibit sparsity due to the
limited number of dominant propagation paths, thus compressed sensing
techniques can be leveraged to conduct channel estimation at mmWave
frequencies. This paper presents a novel approach of constructing beamforming
dictionary matrices for sparse channel estimation using the continuous basis
pursuit (CBP) concept, and proposes two novel low-complexity algorithms to
exploit channel sparsity for adaptively estimating multipath channel parameters
in mmWave channels. We verify the performance of the proposed CBP-based
beamforming dictionary and the two algorithms using a simulator built upon a
three-dimensional mmWave statistical spatial channel model, NYUSIM, that is
based on real-world propagation measurements. Simulation results show that the
CBP-based dictionary offers substantially higher estimation accuracy and
greater spectral efficiency than the grid-based counterpart introduced by
previous researchers, and the algorithms proposed here render better
performance but require less computational effort compared with existing
algorithms.Comment: 7 pages, 5 figures, in 2017 IEEE International Conference on
Communications Workshop (ICCW), Paris, May 201
Beampattern-Based Tracking for Millimeter Wave Communication Systems
We present a tracking algorithm to maintain the communication link between a
base station (BS) and a mobile station (MS) in a millimeter wave (mmWave)
communication system, where antenna arrays are used for beamforming in both the
BS and MS. Downlink transmission is considered, and the tracking is performed
at the MS as it moves relative to the BS. Specifically, we consider the case
that the MS rotates quickly due to hand movement. The algorithm estimates the
angle of arrival (AoA) by using variations in the radiation pattern of the beam
as a function of this angle. Numerical results show that the algorithm achieves
accurate beam alignment when the MS rotates in a wide range of angular speeds.
For example, the algorithm can support angular speeds up to 800 degrees per
second when tracking updates are available every 10 ms.Comment: 6 pages, to be published in Proc. IEEE GLOBECOM 2016, Washington,
D.C., US
Efficient Beam Alignment in Millimeter Wave Systems Using Contextual Bandits
In this paper, we investigate the problem of beam alignment in millimeter
wave (mmWave) systems, and design an optimal algorithm to reduce the overhead.
Specifically, due to directional communications, the transmitter and receiver
beams need to be aligned, which incurs high delay overhead since without a
priori knowledge of the transmitter/receiver location, the search space spans
the entire angular domain. This is further exacerbated under dynamic conditions
(e.g., moving vehicles) where the access to the base station (access point) is
highly dynamic with intermittent on-off periods, requiring more frequent beam
alignment and signal training. To mitigate this issue, we consider an online
stochastic optimization formulation where the goal is to maximize the
directivity gain (i.e., received energy) of the beam alignment policy within a
time period. We exploit the inherent correlation and unimodality properties of
the model, and demonstrate that contextual information improves the
performance. To this end, we propose an equivalent structured Multi-Armed
Bandit model to optimally exploit the exploration-exploitation tradeoff. In
contrast to the classical MAB models, the contextual information makes the
lower bound on regret (i.e., performance loss compared with an oracle policy)
independent of the number of beams. This is a crucial property since the number
of all combinations of beam patterns can be large in transceiver antenna
arrays, especially in massive MIMO systems. We further provide an
asymptotically optimal beam alignment algorithm, and investigate its
performance via simulations.Comment: To Appear in IEEE INFOCOM 2018. arXiv admin note: text overlap with
arXiv:1611.05724 by other author
- …