28 research outputs found
Impact of Residual Transmit RF Impairments on Training-Based MIMO Systems
Radio-frequency (RF) impairments, that exist intimately in wireless
communications systems, can severely degrade the performance of traditional
multiple-input multiple-output (MIMO) systems. Although compensation schemes
can cancel out part of these RF impairments, there still remains a certain
amount of impairments. These residual impairments have fundamental impact on
the MIMO system performance. However, most of the previous works have neglected
this factor. In this paper, a training-based MIMO system with residual transmit
RF impairments (RTRI) is considered. In particular, we derive a new channel
estimator for the proposed model, and find that RTRI can create an irreducible
estimation error floor. Moreover, we show that, in the presence of RTRI, the
optimal training sequence length can be larger than the number of transmit
antennas, especially in the low and high signal-to-noise ratio (SNR) regimes.
An increase in the proposed approximated achievable rate is also observed by
adopting the optimal training sequence length. When the training and data
symbol powers are required to be equal, we demonstrate that, at high SNRs,
systems with RTRI demand more training, whereas at low SNRs, such demands are
nearly the same for all practical levels of RTRI.Comment: Accepted for publication at the IEEE International Conference on
Communications (ICC 2014), 6 pages, 5 figure
Impact of Transceiver Impairments on the Capacity of Dual-Hop Relay Massive MIMO Systems
Despite the deleterious effect of hardware impairments on communication
systems, most prior works have not investigated their impact on widely used
relay systems. Most importantly, the application of inexpensive transceivers,
being prone to hardware impairments, is the most cost-efficient way for the
implementation of massive multiple-input multiple-output (MIMO) systems.
Consequently, the direction of this paper is towards the investigation of the
impact of hardware impairments on MIMO relay networks with large number of
antennas. Specifically, we obtain the general expression for the ergodic
capacity of dual-hop (DH) amplify-and-forward (AF) relay systems. Next, given
the advantages of the free probability (FP) theory with comparison to other
known techniques in the area of large random matrix theory, we pursue a large
limit analysis in terms of number of antennas and users by shedding light to
the behavior of relay systems inflicted by hardware impairments.Comment: 6 pages, 4 figures, accepted in IEEE Global Communications Conference
(GLOBECOM 2015) - Workshop on Massive MIMO: From theory to practice, 201
On the MIMO Capacity with Residual Transceiver Hardware Impairments
Radio-frequency (RF) impairments in the transceiver hardware of communication
systems (e.g., phase noise (PN), high power amplifier (HPA) nonlinearities, or
in-phase/quadrature-phase (I/Q) imbalance) can severely degrade the performance
of traditional multiple-input multiple-output (MIMO) systems. Although
calibration algorithms can partially compensate these impairments, the
remaining distortion still has substantial impact. Despite this, most prior
works have not analyzed this type of distortion. In this paper, we investigate
the impact of residual transceiver hardware impairments on the MIMO system
performance. In particular, we consider a transceiver impairment model, which
has been experimentally validated, and derive analytical ergodic capacity
expressions for both exact and high signal-to-noise ratios (SNRs). We
demonstrate that the capacity saturates in the high-SNR regime, thereby
creating a finite capacity ceiling. We also present a linear approximation for
the ergodic capacity in the low-SNR regime, and show that impairments have only
a second-order impact on the capacity. Furthermore, we analyze the effect of
transceiver impairments on large-scale MIMO systems; interestingly, we prove
that if one increases the number of antennas at one side only, the capacity
behaves similar to the finite-dimensional case. On the contrary, if the number
of antennas on both sides increases with a fixed ratio, the capacity ceiling
vanishes; thus, impairments cause only a bounded offset in the capacity
compared to the ideal transceiver hardware case.Comment: Accepted for publication at the IEEE International Conference on
Communications (ICC 2014), 7 pages, 6 figure
Achievable Rate of Rician Large-Scale MIMO Channels with Transceiver Hardware Impairments
Transceiver hardware impairments (e.g., phase noise,
in-phase/quadrature-phase (I/Q) imbalance, amplifier non-linearities, and
quantization errors) have obvious degradation effects on the performance of
wireless communications. While prior works have improved our knowledge on the
influence of hardware impairments of single-user multiple-input multiple-output
(MIMO) systems over Rayleigh fading channels, an analysis encompassing the
Rician fading channel is not yet available. In this paper, we pursue a detailed
analysis of regular and large-scale (LS) MIMO systems over Rician fading
channels by deriving new, closed-form expressions for the achievable rate to
provide several important insights for practical system design. More
specifically, for regular MIMO systems with hardware impairments, there is
always a finite achievable rate ceiling, which is irrespective of the transmit
power and fading conditions. For LS-MIMO systems, it is interesting to find
that the achievable rate loss depends on the Rician -factor, which reveals
that the favorable propagation in LS-MIMO systems can remove the influence of
hardware impairments. However, we show that the non-ideal LS-MIMO system can
still achieve high spectral efficiency due to its huge degrees of freedom.Comment: 7 pages, 1 table, 3 figures, accepted to appear in IEEE Transactions
on Vehicular Technolog
Hardware Impairments in Large-scale MISO Systems: Energy Efficiency, Estimation, and Capacity Limits
The use of large-scale antenna arrays has the potential to bring substantial
improvements in energy efficiency and/or spectral efficiency to future wireless
systems, due to the greatly improved spatial beamforming resolution. Recent
asymptotic results show that by increasing the number of antennas one can
achieve a large array gain and at the same time naturally decorrelate the user
channels; thus, the available energy can be focused very accurately at the
intended destinations without causing much inter-user interference. Since these
results rely on asymptotics, it is important to investigate whether the
conventional system models are still reasonable in the asymptotic regimes. This
paper analyzes the fundamental limits of large-scale multiple-input
single-output (MISO) communication systems using a generalized system model
that accounts for transceiver hardware impairments. As opposed to the case of
ideal hardware, we show that these practical impairments create finite ceilings
on the estimation accuracy and capacity of large-scale MISO systems.
Surprisingly, the performance is only limited by the hardware at the
single-antenna user terminal, while the impact of impairments at the
large-scale array vanishes asymptotically. Furthermore, we show that an
arbitrarily high energy efficiency can be achieved by reducing the power while
increasing the number of antennas.Comment: Published at International Conference on Digital Signal Processing
(DSP 2013), 6 pages, 5 figure
Designing Wireless Broadband Access for Energy Efficiency: Are Small Cells the Only Answer?
The main usage of cellular networks has changed from voice to data traffic,
mostly requested by static users. In this paper, we analyze how a cellular
network should be designed to provide such wireless broadband access with
maximal energy efficiency (EE). Using stochastic geometry and a detailed power
consumption model, we optimize the density of access points (APs), number of
antennas and users per AP, and transmission power for maximal EE. Small cells
are of course a key technology in this direction, but the analysis shows that
the EE improvement of a small-cell network saturates quickly with the AP
density and then "massive MIMO" techniques can further improve the EE.Comment: Published at Small Cell and 5G Networks (SmallNets) Workshop, IEEE
International Conference on Communications (ICC), 6 pages, 5 figures, 1 tabl
Performance Analysis of Antenna Selection Techniques in MIMO-OFDM System with Hardware Impairments: Energy Efficiency perspective
In this paper we propose a new MIMO-OFDM model in which we consider various antenna selection techniques like Bulk selection and Per-subcarrier selection etc. with hardware impairments such as non-linearties of amplifiers, quantization noise, phase noise and I-Q imbalance etc. As we know that the transceiver hardware impairments limit the channel capacity and the energy efficiency of MIMO-OFDM system, so we can not neglect the fundamental impacts of these hardware impairments {Kappa (0.05 0.1)} on the energy efficiency in the high SNR domain. Therefore we analyze the Energy Efficiency of Bulk and Per-subcarrier antenna selection techniques with or without hardware impairments. It has been observed that the energy efficiency decreases as the value of these hardware impairments increases. As we compared the Bulk antenna selection with the Per-subcarrier antenna selection scheme, the Per-subcarrier antenna selection requires more number of RF (radio frequency) chains and transmits power in comparison to the Bulk selection. Due to this, the Bulk antenna selection technique is more energy efficient than Per-subcarrier antenna selection
Simultaneous Information and Power Transfer with Transmitters with Hardware Impairments
We investigate the performance of a communication system with simultaneous wireless information and power transfer capabilities under non-ideal transmitter hardware. We adopt an experimentally validated additive noise model in which the level of the noise at an antenna is proportional to the signal power at that antenna. We consider the linear precoder design problem and focus on the problem of minimizing the mean-square error under energy harvesting constraints. This set-up, in general, constitutes a non-convex formulation. For the single antenna information user case, we provide a tight convex relaxation, i.e. a convex formulation from which an optimal solution for the original problem can be constructed. For the general case, we propose a block coordinate descent technique to solve the resulting non-convex problem. Our numerical results illustrate the effect of hardware impairments on the system