669 research outputs found
On the MIMO Channel Capacity of Multi-Dimensional Signal Sets
In this contribution we evaluate the capacity of Multi-Input Multi-Output (MIMO) systems using multi-dimensional PSK/QAM signal sets. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and the AWGN channel. However, since this gap becomes narrower when the receiver diversity order is increased, for higher-order receiver diversity the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable throughput than the corresponding MIMO system designed for full diversity gain, although this is attained at the cost of a higher complexity and a higher SNR. The tradeoffs between diversity gain, multiplexing gain, complexity and bandwidth are studied
Sum Rate and Fairness Analysis for the MU-MIMO Downlink under PSK Signalling: Interference Suppression vs Exploitation
In this paper, we analyze the sum rate performance of multi-user
multiple-input multiple-output (MU-MIMO) systems, with a finite constellation
phase-shift keying (PSK) input alphabet. We analytically calculate and compare
the achievable sum rate in three downlink transmission scenarios: 1) without
precoding, 2) with zero forcing (ZF) precoding 3) with closed form constructive
interference (CI) precoding technique. In light of this, new analytical
expressions for the average sum rate are derived in the three cases, and Monte
Carlo simulations are provided throughout to validate the analysis.
Furthermore, based on the derived expressions, a power allocation scheme that
can ensure fairness among the users is also proposed. The results in this work
demonstrate that, the CI strictly outperforms the other two schemes, and the
performance gap between the considered schemes increases with increase in the
MIMO size. In addition, the CI provides higher fairness and the power
allocation algorithm proposed in this paper can achieve maximum fairness index
Asymptotic Analysis of SU-MIMO Channels With Transmitter Noise and Mismatched Joint Decoding
Hardware impairments in radio-frequency components of a wireless system cause
unavoidable distortions to transmission that are not captured by the
conventional linear channel model. In this paper, a 'binoisy' single-user
multiple-input multiple-output (SU-MIMO) relation is considered where the
additional distortions are modeled via an additive noise term at the transmit
side. Through this extended SU-MIMO channel model, the effects of transceiver
hardware impairments on the achievable rate of multi-antenna point-to-point
systems are studied. Channel input distributions encompassing practical
discrete modulation schemes, such as, QAM and PSK, as well as Gaussian
signaling are covered. In addition, the impact of mismatched detection and
decoding when the receiver has insufficient information about the
non-idealities is investigated. The numerical results show that for realistic
system parameters, the effects of transmit-side noise and mismatched decoding
become significant only at high modulation orders.Comment: 16 pages, 7 figure
A universal space-time architecture for multiple-antenna aided systems
In this tutorial, we first review the family of conventional multiple-antenna techniques, and then we provide a general overview of the recent concept of the powerful Multiple-Input Multiple-Output (MIMO) family based on a universal Space-Time Shift Keying (STSK) philosophy. When appropriately configured, the proposed STSK scheme has the potential of outperforming conventional MIMO arrangements
Low SNR Capacity of Noncoherent Fading Channels
Discrete-time Rayleigh fading single-input single-output (SISO) and
multiple-input multiple-output (MIMO) channels are considered, with no channel
state information at the transmitter or the receiver. The fading is assumed to
be stationary and correlated in time, but independent from antenna to antenna.
Peak-power and average-power constraints are imposed on the transmit antennas.
For MIMO channels, these constraints are either imposed on the sum over
antennas, or on each individual antenna. For SISO channels and MIMO channels
with sum power constraints, the asymptotic capacity as the peak signal-to-noise
ratio tends to zero is identified; for MIMO channels with individual power
constraints, this asymptotic capacity is obtained for a class of channels
called transmit separable channels. The results for MIMO channels with
individual power constraints are carried over to SISO channels with delay
spread (i.e. frequency selective fading).Comment: submitted to IEEE I
Spatial Multiplexing of QPSK Signals with a Single Radio: Antenna Design and Over-the-Air Experiments
The paper describes the implementation and performance analysis of the first
fully-operational beam-space MIMO antenna for the spatial multiplexing of two
QPSK streams. The antenna is composed of a planar three-port radiator with two
varactor diodes terminating the passive ports. Pattern reconfiguration is used
to encode the MIMO information onto orthogonal virtual basis patterns in the
far-field. A measurement campaign was conducted to compare the performance of
the beam-space MIMO system with a conventional 2-by-?2 MIMO system under
realistic propagation conditions. Propagation measurements were conducted for
both systems and the mutual information and symbol error rates were estimated
from Monte-Carlo simulations over the measured channel matrices. The results
show the beam-space MIMO system and the conventional MIMO system exhibit
similar finite-constellation capacity and error performance in NLOS scenarios
when there is sufficient scattering in the channel. In comparison, in LOS
channels, the capacity performance is observed to depend on the relative
polarization of the receiving antennas.Comment: 31 pages, 23 figure
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