19 research outputs found
Asymptotic SER and Outage Probability of MIMO MRC in Correlated Fading
This letter derives the asymptotic symbol error rate (SER) and outage
probability of multiple-input multiple-output (MIMO) maximum ratio combining
(MRC) systems. We consider Rayleigh fading channels with both transmit and
receive spatial correlation. Our results are based on new asymptotic
expressions which we derive for the p.d.f. and c.d.f. of the maximum eigenvalue
of positive-definite quadratic forms in complex Gaussian matrices. We prove
that spatial correlation does not affect the diversity order, but that it
reduces the array gain and hence increases the SER in the high SNR regime.Comment: 10 pages, 2 figures, to appear in IEEE Signal Processing Letter
Downlink Energy Efficiency Analysis of Some Multiple Antenna Systems
In this paper we compare the energy efficiency of different multiple antenna transmission schemes for long-range wireless networks, assuming a realistic power consumption model. We consider the downlink, between a base station and a mobile station, in which the Alamouti scheme, transmit beamforming, receive diversity, spatial multiplexing, and transmit antenna selection are compared. Our analysis shows that, for different types of base stations, outage probability requirements and spectral efficiencies, the transmit antenna selection scheme is in general the most energy efficient option. Although antenna selection is not the best in terms of outage probability, it becomes the most efficient in terms of overall power consumption as it requires a single radio-frequency chain to obtain spatial diversity
Performance Analysis of MIMO-MRC in Double-Correlated Rayleigh Environments
We consider multiple-input multiple-output (MIMO) transmit beamforming
systems with maximum ratio combining (MRC) receivers. The operating environment
is Rayleigh-fading with both transmit and receive spatial correlation. We
present exact expressions for the probability density function (p.d.f.) of the
output signal-to-noise ratio (SNR), as well as the system outage probability.
The results are based on explicit closed-form expressions which we derive for
the p.d.f. and c.d.f. of the maximum eigenvalue of double-correlated complex
Wishart matrices. For systems with two antennas at either the transmitter or
the receiver, we also derive exact closed-form expressions for the symbol error
rate (SER). The new expressions are used to prove that MIMO-MRC achieves the
maximum available spatial diversity order, and to demonstrate the effect of
spatial correlation. The analysis is validated through comparison with
Monte-Carlo simulations.Comment: 25 pages. Submitted to the IEEE Transactions on Communication
Beamforming in MISO Systems: Empirical Results and EVM-based Analysis
We present an analytical, simulation, and experimental-based study of
beamforming Multiple Input Single Output (MISO) systems. We analyze the
performance of beamforming MISO systems taking into account implementation
complexity and effects of imperfect channel estimate, delayed feedback, real
Radio Frequency (RF) hardware, and imperfect timing synchronization. Our
results show that efficient implementation of codebook-based beamforming MISO
systems with good performance is feasible in the presence of channel and
implementation-induced imperfections. As part of our study we develop a
framework for Average Error Vector Magnitude Squared (AEVMS)-based analysis of
beamforming MISO systems which facilitates comparison of analytical,
simulation, and experimental results on the same scale. In addition, AEVMS
allows fair comparison of experimental results obtained from different wireless
testbeds. We derive novel expressions for the AEVMS of beamforming MISO systems
and show how the AEVMS relates to important system characteristics like the
diversity gain, coding gain, and error floor.Comment: Submitted to IEEE Transactions on Wireless Communications, November
200
Resource allocation for maximizing outage throughput in OFDMA systems with finite-rate feedback
Previous works on orthogonal frequency division multiple access (OFDMA) systems with quantized channel state information (CSI) were mainly based on suboptimal quantization methods. In this paper, we consider the performance limit of OFDMA systems with quantized CSI over independent Rayleigh fading channels using the rate-distortion theory. First, we establish a lower bound on the capacity of the feedback channel and build the test channel that achieves this lower bound. Then, with the derived test channel, we characterize the system performance with the outage throughput and formulate the outage throughput maximization problem with quantized channel state information (CSI). To solve this problem in low complexity, we develop a suboptimal algorithm that performs resource allocation in two steps: subcarrier allocation and power allocation. Using this approach, we can numerically evaluate the outage throughput in terms of feedback rate. Numerical results show that this suboptimal algorithm can provide a near optimal performance (with a performance loss of less than 5%) and the outage throughput with a limited feedback rate can be close to that with perfect CSI.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000294918800001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicTelecommunicationsSCI(E)1ARTICLEnul
DeepTx: Deep Learning Beamforming with Channel Prediction
Machine learning algorithms have recently been considered for many tasks in
the field of wireless communications. Previously, we have proposed the use of a
deep fully convolutional neural network (CNN) for receiver processing and shown
it to provide considerable performance gains. In this study, we focus on
machine learning algorithms for the transmitter. In particular, we consider
beamforming and propose a CNN which, for a given uplink channel estimate as
input, outputs downlink channel information to be used for beamforming. The CNN
is trained in a supervised manner considering both uplink and downlink
transmissions with a loss function that is based on UE receiver performance.
The main task of the neural network is to predict the channel evolution between
uplink and downlink slots, but it can also learn to handle inefficiencies and
errors in the whole chain, including the actual beamforming phase. The provided
numerical experiments demonstrate the improved beamforming performance.Comment: 27 pages, this work has been submitted to the IEEE for possible
publication; v2: Fixed typo in author name, v3: a revisio
Design and testing methodologies for signal processing systems using DICE
The design and integration of embedded systems in heterogeneous programming environments is still largely done in an ad hoc fashion making the overall development process more complicated, tedious and error-prone. In this work, we propose enhancements to existing design flows that utilize model-based design to verify cross-platform correctness of individual actors. The DSPCAD Integrative Command Line Environment (DICE) is a realization of managing these enhancements.
We demonstrate this design flow with two case studies. By using DICE's novel test framework on modules of a triggering system in the Large Hadron Collider, we demonstrate how the cross-platform model-based approach, automatic testbench creation and integration of testing in the design process alleviate the rigors of developing such a complex digital system. The second case study is an exploration study into the required precision for eigenvalue decomposition using the Jacobi algorithm. This case study is a demonstration of the use of dataflow modeling in early stage application exploration and the use of DICE in the overall design flow
Energy Efficiency Analysis of Two-Tier MIMO Diversity Schemes in Poisson Cellular Networks
In this paper, the energy efficiency (EE) of different MIMO diversity schemes is analyzed for the downlink of a two-tier network consisting of both macro- and femto-cells. The locations of the base stations (BSs) in both tiers are modeled by spatial Poisson point processes (PPPs). The EE of the system in b/J/Hz is obtained for different antenna configurations under various diversity schemes. Adaptive modulation is employed to maximize both the throughput and the EE across both tiers. Borrowing well established tools from stochastic geometry, we obtain closed-form expressions for the coverage, throughput, and power consumption for a two tier rate adaptive cellular network. Building on the developed analytical framework, we formulate the resource allocation problem for each diversity scheme with the aim of maximizing the network-wide EE while satisfying a minimum QoS in each tier. We consider that both the number of antennas and the spectrum allocated to each tier constitute the network resource which must be efficiently selected for both tiers to maximize network-wide performance. The best performance in terms of the EE is provided by the schemes which strike a good balance between the achievable maximum throughput and the consumed power (both increasing with the number of RF chains used). In addition, the potential savings in EE by using femto-cells with sleeping mode capabilities are analyzed. It is observed that, when the density of active co-channel femto-cells exceeds a certain threshold, the EE of the system can be significantly improved by sleep scheduling