10,763 research outputs found
Beam Management for Millimeter Wave Beamspace MU-MIMO Systems
Millimeter wave (mmWave) communication has attracted increasing attention as
a promising technology for 5G networks. One of the key architectural features
of mmWave is the use of massive antenna arrays at both the transmitter and the
receiver sides. Therefore, by employing directional beamforming (BF), both
mmWave base stations (MBSs) and mmWave users (MUEs) are capable of supporting
multi-beam simultaneous transmissions. However, most researches have only
considered a single beam, which means that they do not make full potential of
mmWave. In this context, in order to improve the performance of short-range
indoor mmWave networks with multiple reflections, we investigate the challenges
and potential solutions of downlink multi-user multi-beam transmission, which
can be described as a high-dimensional (i.e., beamspace) multi-user
multiple-input multiple-output (MU-MIMO) technique, including multi-user BF
training, simultaneous users' grouping, and multi-user multibeam power
allocation. Furthermore, we present the theoretical and numerical results to
demonstrate that beamspace MU-MIMO compared with single beam transmission can
largely improve the rate performance of mmWave systems.Comment: The sixth IEEE/CIC International Conference on Communications in
China (ICCC2017
Non-commutative Geometry Modified Non-Gaussianities of Cosmological Perturbation
We investigate the noncommutative effect on the non-Gaussianities of
primordial cosmological perturbation. In the lowest order of string length and
slow-roll parameter, we find that in the models with small speed of sound the
noncommutative modifications could be observable if assuming a relatively low
string scale. In particular, the dominant modification of non-Gaussianity
estimator f_{NL} could reach O(1) in DBI inflation and K-inflation. The
corrections are sensitive to the speed of sound and the choice of string length
scale. Moreover the shapes of the corrected non-Gaussianities are distinct from
that of ordinary ones.Comment: 26 pages, 3 figures Added references, changed conten
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