4,600 research outputs found
Performance Gains of Optimal Antenna Deployment for Massive MIMO Systems
We consider the uplink of a single-cell multi-user multiple-input
multiple-output (MIMO) system with several single antenna transmitters/users
and one base station with antennas in the regime. The
base station antennas are evenly distributed to admissable locations
throughout the cell.
First, we show that a reliable (per-user) rate of is achievable
through optimal locational optimization of base station antennas. We also prove
that an rate is the best possible. Therefore, in contrast to a
centralized or circular deployment, where the achievable rate is at most a
constant, the rate with a general deployment can grow logarithmically with ,
resulting in a certain form of "macromultiplexing gain."
Second, using tools from high-resolution quantization theory, we derive an
accurate formula for the best achievable rate given any and any user
density function. According to our formula, the dependence of the optimal rate
on the user density function is curiously only through the differential
entropy of . In fact, the optimal rate decreases linearly with the
differential entropy, and the worst-case scenario is a uniform user density.
Numerical simulations confirm our analytical findings.Comment: GLOBECOM 201
Adaptive Multicell 3D Beamforming in Multi-Antenna Cellular Networks
We consider a cellular network with multi-antenna base stations (BSs) and
single-antenna users, multicell cooperation, imperfect channel state
information, and directional antennas each with a vertically adjustable beam.
We investigate the impact of the elevation angle of the BS antenna pattern,
denoted as tilt, on the performance of the considered network when employing
either a conventional single-cell transmission or a fully cooperative multicell
transmission. Using the results of this investigation, we propose a novel
hybrid multicell cooperation technique in which the intercell interference is
controlled via either cooperative beamforming in the horizontal plane or
coordinated beamfroming in the vertical plane of the wireless channel, denoted
as adaptive multicell 3D beamforming. The main idea is to divide the coverage
area into two disjoint vertical regions and adapt the multicell cooperation
strategy at the BSs when serving each region. A fair scheduler is used to share
the time-slots between the vertical regions. It is shown that the proposed
technique can achieve performance comparable to that of a fully cooperative
transmission but with a significantly lower complexity and signaling
requirements. To make the performance analysis computationally efficient,
analytical expressions for the user ergodic rates under different beamforming
strategies are also derived.Comment: Accepted for publication in IEEE Transaction on Vehicular Technolog
Preliminary Results on 3D Channel Modeling: From Theory to Standardization
Three dimensional beamforming (3D) (also elevation beamforming) is now
gaining a growing interest among researchers in wireless communication. The
reason can be attributed to its potential to enable a variety of strategies
like sector or user specific elevation beamforming and cell-splitting. Since
these techniques cannot be directly supported by current LTE releases, the 3GPP
is now working on defining the required technical specifications. In
particular, a large effort is currently made to get accurate 3D channel models
that support the elevation dimension. This step is necessary as it will
evaluate the potential of 3D and FD(Full Dimensional) beamforming techniques to
benefit from the richness of real channels. This work aims at presenting the
on-going 3GPP study item "Study on 3D-channel model for Elevation Beamforming
and FD-MIMO studies for LTE", and positioning it with respect to previous
standardization works
Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays
Massive MIMO (multiple-input multiple-output) is no longer a "wild" or
"promising" concept for future cellular networks - in 2018 it became a reality.
Base stations (BSs) with 64 fully digital transceiver chains were commercially
deployed in several countries, the key ingredients of Massive MIMO have made it
into the 5G standard, the signal processing methods required to achieve
unprecedented spectral efficiency have been developed, and the limitation due
to pilot contamination has been resolved. Even the development of fully digital
Massive MIMO arrays for mmWave frequencies - once viewed prohibitively
complicated and costly - is well underway. In a few years, Massive MIMO with
fully digital transceivers will be a mainstream feature at both sub-6 GHz and
mmWave frequencies. In this paper, we explain how the first chapter of the
Massive MIMO research saga has come to an end, while the story has just begun.
The coming wide-scale deployment of BSs with massive antenna arrays opens the
door to a brand new world where spatial processing capabilities are
omnipresent. In addition to mobile broadband services, the antennas can be used
for other communication applications, such as low-power machine-type or
ultra-reliable communications, as well as non-communication applications such
as radar, sensing and positioning. We outline five new Massive MIMO related
research directions: Extremely large aperture arrays, Holographic Massive MIMO,
Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive
MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin
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