Capacity bounds and estimates for the finite scatterers MIMO wireless channel (original) (raw)

Correlated MIMO Wireless Channels: Capacity, Optimal Signaling, and Asymptotics

IEEE Transactions on Information Theory, 2005

The capacity of the multiple-input multiple-output (MIMO) wireless channel with uniform linear arrays (ULAs) of antennas at the transmitter and receiver is investigated. It is assumed that the receiver knows the channel perfectly but that the transmitter knows only the channel statistics. The analysis is carried out using an equivalent virtual representation of the channel that is obtained via a spatial discrete Fourier transform. A key property of the virtual representation that is exploited is that the components of virtual channel matrix are approximately independent. With this approximation, the virtual representation allows for a general capacity analysis without the common simplifying assumptions of Gaussian statistics and product-form correlation (Kronecker model) for the channel matrix elements. A deterministic line-of-sight (LOS) component in the channel is also easily incorporated in much of the analysis. It is shown that in the virtual domain, the capacity-achieving input vector consists of independent zero-mean proper-complex Gaussian entries, whose variances can be computed numerically using standard convex programming algorithms based on the channel statistics. Furthermore, in the asymptotic regime of low signal-to-noise ratio (SNR), it is shown that beamforming along one virtual transmit angle is asymptotically optimal. Necessary and sufficient conditions for the optimality of beamforming, and the value of the corresponding optimal virtual angle, are also derived based on only the second moments of the virtual channel coefficients. Numerical results indicate that beamforming may be close to optimum even at moderate values of SNR for sparse scattering environments. Finally, the capacity is investigated in the asymptotic regime where the numbers of receive and transmit antennas go to infinity, with their ratio being kept constant. Using a result of Girko, an expression for the asymptotic capacity scaling with the number of antennas is obtained in terms of the two-dimensional spatial scattering function of the channel. This asymptotic formula for the capacity is shown to be accurate even for small numbers of transmit and receive antennas in numerical examples.

On the MIMO channel capacity of multidimensional signal sets

IEEE Transactions on Vehicular Technology, 2006

In this contribution two general formulae were derived for the capacity evaluation of Multi-Input Multi-Output (MIMO) systems using multi-dimensional signal sets, different modulation schemes and an arbitrary number of transmit as well as receive antennas. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleighfading 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 capacity, than the corresponding MIMO system designed for achieving full diversity gain, provided that the channel SNR is sufficiently high.

Capacity of MIMO system with finite scattering in the presence of interference

2004

This paper investigates the up-link capacity of a multiple-input multiple-output (MIMO) wireless channel subject to finite multipath scattering in the presence of cochannel interference (CCI). We first consider single interferers with fixed position and then extend to cellular systems. We observe that the average capacity of MIMO system in the presence of interference is significantly greater than that of a single-input single-output (SISO) system and a single-output multiple-output (SIMO) system at moderate SNRs. It is presented that the link capacity of a MIMO system could be maximised by means of a spatiallywhitened matched filter, which converts the interference uncorrelated between receive antennas. It is shown that the capacity of the finite scatterers channel can be even larger than that of the independent Rayleigh channel through the use of spatial pre-whitening filter.

Asymptotic Capacity of Multi-User MIMO Communications

2013

Abstract—This paper introduces two new formulas to derive explicit capacity expressions of a class of communication schemes, which include single-cell multi-user MIMO and singleuser MIMO with multi-cell interference. The extension of a classical theorem from Silverstein allows us to assume a channel Kronecker model between the base stations and the cellular terminals, provided that they all embed a large number of antennas. As an introductory example, we study the singleuser MIMO setting with multi-cell interference, in the downlink. We provide new asymptotic capacity formulas when single-user decoding of the incoming data or MMSE decoding are used. Simulations are shown to corroborate the theoretical claims, even when the number of transmit/receive antennas is not very large. I.

Introducing 'space' into space-time MIMO capacity calculations: a new closed form upper bound

International Conference on Telecommunications, 2003

We present a new upper bound on capacity for multiple-input multiple-output (MIMO) wireless fading channels, which is more general and realistic than previous capacity expressions. By including spatial information at the antenna arrays, a closed form upper bound on capacity, which uses the physics of signal propagation combined with statistics of the scattering environment, is derived. This expression gave the

The Ideal MIMO Channel: Maximizing Capacity in Sparse Multipath with Reconfigurable Arrays

2006 IEEE International Symposium on Information Theory, 2006

While the intense research on multi-antenna (MIMO) wireless communication channels was pioneered by results based on an i.i.d. channel model representing a rich multipath environment, there is growing experimental evidence that physical wireless channels exhibit a sparse multipath structure, even at relatively low antenna dimensions. In this paper, we propose a model for sparse multipath channels and study coherent MIMO capacity as a function of SNR for a fixed number of antennas. In a recent work, we had shown that the spatial distribution of the sparse multipath has a significant impact on capacity and had also characterized the optimal distribution (the Ideal MIMO Channel) that maximizes capacity at any operating SNR. In this paper, we refine these results and develop a framework for maximizing MIMO capacity at any SNR by systematically adapting the array configurations (antenna spacings) at the transmitter and receiver to the level of sparsity. Surprisingly, three canonical array configurations are sufficient for near-optimum performance over the entire SNR range. In a scattering environment with randomly distributed paths, the capacity gain due to optimal configuration is directly proportional to the number of antennas at low SNR's. Numerical results based on a realistic physical model are presented to illustrate capacity gains with reconfigurable antenna arrays.

On the asymptotic capacity of MIMO systems with antenna arrays of fixed length

IEEE Transactions on Wireless Communications, 2005

Previous authors have shown that the asymptotic capacity of a multiple element antenna (MEA) system with ¢ transmit and ¢ receive antennas (termed an £ ¤ ¢ ¦ ¥ § ¢ © MEA) grows linearly with ¢ if, for all , the correlation of the fading for two antenna elements whose indices differ by remains fixed as antennas are added to the array. However, in practice, the total size of the array is often fixed, and thus the correlation of the fading for two elements separated in index by some value will change as the number of antenna elements is increased. In this paper, under the condition that the size of an array of antennas is fixed, and assuming that the transmitter does not have access to the channel state information (CSI) while the receiver has perfect CSI, the asymptotic properties of the instantaneous mutual information of an £ ¤ ¢ ¥ § ¢ © MEA wireless system in a quasi-static fading channel are derived analytically and tested for accuracy for finite ¢ through simulations. For many channel correlation structures, it is demonstrated that the asymptotic performance converges almost surely, implying that such MEA systems have a certain strong robustness to the instantiation of the channel fading values.

On the MIMO Channel Capacity Predicted by Kronecker and Müller Models

Wireless Personal Communications, 2008

This paper presents a comparison between the outage capacity of MIMO channels predicted by the Kronecker and Müller models as a function of the number of scatterers, transmit and receive antennas. The Müller model is based on the singly-scattered rays between arrays of transmit- and receive antennas, while the Kronecker model considers only double scattering. The channel capacity predictions by the Müller model were observed to be higher than those by the Kronecker model. Moreover, Müller model is simpler since it is characterized by fewer parameters, and accounts for frequency selective fading whilst the Kronecker model is valid only for frequency flat fading.