155 research outputs found
Capacity of MIMO Channels: asymptotic evaluation under correlated fading
This paper investigates the asymptotic uniform power allocation capacity of frequency nonselective multiple-input
multiple-output channels with fading correlation at either the
transmitter or the receiver. We consider the asymptotic situation,
where the number of inputs and outputs increase without bound
at the same rate. A simple uniparametric model for the fading
correlation function is proposed and the asymptotic capacity per
antenna is derived in closed form. Although the proposed correlation
model is introduced only for mathematical convenience, it
is shown that its shape is very close to an exponentially decaying
correlation function. The asymptotic expression obtained provides
a simple and yet useful way of relating the actual fading
correlation to the asymptotic capacity per antenna from a purely
analytical point of view. For example, the asymptotic expressions
indicate that fading correlation is more harmful when arising at
the side with less antennas. Moreover, fading correlation does not
influence the rate of growth of the asymptotic capacity per receive
antenna with high Eb /N0.Peer Reviewe
Modeling of wide-band MIMO radio channels based on NLoS indoor measurements
Link to published version (if available)
Linear MIMO Precoding in Jointly-Correlated Fading Multiple Access Channels with Finite Alphabet Signaling
In this paper, we investigate the design of linear precoders for
multiple-input multiple-output (MIMO) multiple access channels (MAC). We assume
that statistical channel state information (CSI) is available at the
transmitters and consider the problem under the practical finite alphabet input
assumption. First, we derive an asymptotic (in the large-system limit) weighted
sum rate (WSR) expression for the MIMO MAC with finite alphabet inputs and
general jointly-correlated fading. Subsequently, we obtain necessary conditions
for linear precoders maximizing the asymptotic WSR and propose an iterative
algorithm for determining the precoders of all users. In the proposed
algorithm, the search space of each user for designing the precoding matrices
is its own modulation set. This significantly reduces the dimension of the
search space for finding the precoding matrices of all users compared to the
conventional precoding design for the MIMO MAC with finite alphabet inputs,
where the search space is the combination of the modulation sets of all users.
As a result, the proposed algorithm decreases the computational complexity for
MIMO MAC precoding design with finite alphabet inputs by several orders of
magnitude. Simulation results for finite alphabet signalling indicate that the
proposed iterative algorithm achieves significant performance gains over
existing precoder designs, including the precoder design based on the Gaussian
input assumption, in terms of both the sum rate and the coded bit error rate.Comment: 7 pages, 2 figures, accepted for ICC1
Antenna matching for capacity maximization in compact MIMO systems
As MIMO technology slowly matures, it is finding its way into more wireless applications. However, some important applications, including mobile communications, require compact implementations. One important challenge in miniaturizing MIMO systems for compact terminals is to overcome capacity performance degradation resulting from mutual coupling among closely separated antennas. In this contribution, we begin with a review of the state-of-the-art, with particular emphasis on impedance matching and its impact on capacity. Whereas it has been shown that a multiport extension of the conjugate match is optimum in a reference environment with uniform 3D angular power spectrum, its bandwidth is severely reduced by decreasing antenna separation. On the other hand, noncoupled, individual port matching is inherently simpler to implement and broader in bandwidth, but offers a smaller capacity. Here, we demonstrate that mean capacity can be easily maximized with respect to individual port matching in a given random field. The extent of capacity gains provided by the optimized matching network over existing individual port matching networks strongly depends on the propagation environment
Multi-Panel Sparse Base Station Design with Physical Antenna Effects in Massive MU-MIMO
A novel base station antenna (BSA) configuration is presented to mitigate degrading physical antenna effects in massive multiple-input multiple-output (MIMO) systems, while minimizing implementation complexities. Instead of using a commonly considered single antenna panel comprising of many elements covering a wide field-of-view (FOV) of 120 degrees, L tilted panels are used employing L times fewer elements and L times smaller FOV per panel. The spatial resolution of each panel is enhanced by employing sparse arrays with suppressed (grating-lobe) radiation outside its corresponding FOV. Therefore, more directive antenna elements can be deployed in each panel to compensate for the effective isotropic radiated power (EIRP) reduction. While sectorisation reduces the antenna gain variation in 120 degrees FOV, cooperation among multiple panels in downlink beamforming is seen to be capable of inter-panel interference suppression for sum-rate enhancement. A network model is used as a multi-user (MU) MIMO simulator incorporating both antenna and channel effects. It is shown that when the number of base station antennas is ten times the number of users, the average downlink sum-rate in pure line-of-sight (LOS), rich and poor multipath environments is increased up to 60.2%, 23% and 11.1%, respectively, by multi-panel sparse arrays applying zero-forcing (ZF) precoding
Design and analysis of multi-element antenna systems and agile radiofrequency frontends for automotive applications
Vehicular connectivity serves as one of the major enabling technologies for
current applications like driver assistance, safety and infotainment as well as
upcoming features like highly automated vehicles - all of which having certain
quality of service requirements, e. g. datarate or reliability. This work focuses on
vehicular integration of multiple-input-multiple-output (MIMO) capable multielement
antenna systems and frequency-agile radio frequency (RF) front ends
to cover current and upcoming connectivity needs. It is divided in four major
parts. For each part, mostly physical layer effects are analyzed (any performance
lost on physical layer, cannot be compensated in higher layers), sensitivities are
identified and novel concepts are introduced based on the status-quo findings.Fahrzeugvernetzung dient als eine der wesentlichsten Befähigungstechnologien
fĂĽr moderne Fahrerassistenzsysteme und zukĂĽnftig auch hochautomatisiertes
Fahren. Sowohl die heutigen als auch zukĂĽnftige Anwendungen haben besondere
Dienstgüteanforderungen, z.B. in Bezug auf die Datenrate oder Verlässlichkeit.
Im Rahmen dieser Arbeit wird die Integration von Mehrantennensystemen fĂĽr
MIMO-Funkanwendungen (MIMO: engl. Multiple Input Multiple Output) sowie
von frequenzagilen Hochfrequenzfrontends im Fahrzeugumfeld untersucht, um
so eine technische Grundlage fĂĽr zukĂĽnftige Anforderungen an die automobile
Vernetzung anbieten zu können. Die dabei gewonnenen Erkenntnisse lassen sich
in vier Teile gliedern. Grundsätzlich konzentrieren sich die Untersuchungen vorrangig
auf die physikalische Ebene. Auf Basis des aktuellen Status Quo werden
Sensitivitäten herausgearbeitet, neue Konzepte hergeleitet und entwickelt
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