Analysis and performance of some basic space-time architectures (original) (raw)

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.

A stratified diagonal layered space-time architecture: Information theoretic and signal processing a

IEEE Transactions on Signal Processing

We consider a multielement antenna system that uses transmit and receive antennas [an (M,N) wireless link] impaired by additive white Gaussian noise in a quasistatic flat-fading channel environment. The transmitter, which is subject to a power constraint, does not know the random outcome of the matrix channel but does know the channel statistics. The link operates under a probability of outage constraint. We present a novel architecture using stratified space-time diagonals to express a message for efficient communications. The special message arrangement, which is termed stratified-diagonal-BLAST (SD-BLAST), enables receiver signal processing that substantially mutes self interference caused by multipath without incurring waste of space-time. We investigate the proposed communication structure in important downlink categories, showing that, in theory, the message architecture is optimally efficient for all ( , 1) systems and extremely efficient when . We quantify the capacity performance of SD-BLAST using empirically generated complementary cumulative distribution functions (CCDFs) for (16, 5), (8, 3), and (4, 2) systems to exhibit near optimal performance most especially for the (16, 5) system.

Stratified diagonal layered space-time architectures: signal processing and information theoretic aspects

IEEE Transactions on Signal Processing, 2003

Special Issue: Multiple-Input Multiple-Output (MIMO) Communications

Wireless Communications and Mobile Computing, 2004

The idea of using multiple transmit and receive antennas in wireless communication systems is one of the most important breakthroughs in communication theory during the last decade. Popularly referred to as MIMO technology, this concept can greatly improve data throughput and link performance in wireless networks. In principle, a MIMO system can operate in, or anywhere between, one of the two possible modes. If the transmitter knows the channel, then one can use spatial beamforming techniques to steer RF energy in the direction of the receiver. On the other hand, if the transmitter does not know the channel, one can use space-time coding which effectively distributes the transmitted power uniformly in all directions, and in addition augments the data with structure that can be used to combat from fading dips. Sometimes, space-time coding methods are grouped into two categories: those that focus on throughput improvement (e.g. Bell-Labs layered space-time architecture, BLAST), and those that solely aim at improving link performance (including, most notably, orthogonal block coding and transmit diversity schemes); however, this classification is simplistic and many of the currently best known schemes do not fall under any of these two groups.

Capacity of space-time wireless channels: a physical perspective

Manufacturing Engineer

Existing results on MIMO channel capacity assume a rich scattering environment in which the channel power scales quadratically with the number of antennas, resulting in linear capacity scaling with the number of antennas. However, such scaling in channel power is physically impossible indefinitely. We thus address the following fundamental question: For a given channel power scaling law, what is the best achievable capacity scaling law? For a channel power scaling, ρ c (N) = O(N γ), γ ∈ (0, 2], we argue that the channel capacity cannot scale faster than C(N) = O(ρ c (N)) = O(N γ/2). Our approach is based on a family of space-time channels corresponding to different distributions of channel power in the spatial signal space dimensions. We develop the concept of an ideal MIMO channel that achieves the optimal scaling law for a given ρ c (N). For a given number of antennas, unlike existing results that either emphasize the low or high SNR regimes, we propose a methodology for capacity-optimal signaling at any SNR. The methodology is based on creating the ideal channel from any given physical scattering environment via adaptive-resolution array configurations.

Spatially and temporally correlated MIMO channels: modeling and capacity analysis

IEEE Transactions on Vehicular Technology, 2004

Wireless communication systems employing multiple antennas at both the transmitter and receiver have been shown to offer significant gains over single-antenna systems. Recent studies on the capacity of multiple-input-multiple-output (MIMO) channels have focused on the effect of spatial correlation. The joint effect of spatial and temporal correlation has not been well studied. In this paper, a geometric MIMO channel model is presented, which considers motion of the receiver and nonisotropic scattering at both ends of the radio link. A joint space-time cross-correlation function is derived from this model and variates with this joint correlation are generated by using the vector autoregressive stochastic model. The outage capacity of this channel is considered where the effects of antenna spacing, antenna array angle, degree of nonisotropic scattering, and receiver motion are investigated. When transmit and receive antennas are employed, it is shown that the outage capacity still increases linearly with respect to , despite the presence of spatial and temporal correlation. Furthermore, analytical expressions are derived for the ergodic capacity of a MIMO channel for the cases of spatial correlation at one end and at both ends of the radio link. The latter case does not lend itself to numerical evaluation, but the former case is shown to be accurate by comparison with simulation results. The proposed analysis is very general, as it is based on the transmit and receive antenna correlations matrices.

Achieving MIMO channel capacity using multirate layered space-time coding architectures

Gastroenterology, 2005

We propose a multirate diagonal space-time interleaved (DSTI) coded modulation system with a low complexity linear successive decoding and interference cancellation receiver for quasi-static Rayleigh fading multiple-input multiple-output (MIMO) channels. In comparison with the traditional BLAST architecture, the proposed multirate DSTI system has more practical virtues while achieving near capacity performance for sufficiently large multiple antennas. The key findings of this paper are: (i) the derivation of the probability density functions of per-layer mutual informations, which can be used to estimate per-layer rates, and (ii) the design of multirate DSTI system using punctured turbo codes. Simulation results show significant gains in packet error-rate (PER) performances.

Capacity and performance analysis of space-time block coded MIMO systems with receive antenna selection in Rayleigh fading channels

IET-UK International Conference on Information and Communication Technology in Electrical Sciences (ICTES 2007), 2007

Multi-Antenna systems are expected to play very important role in future multimedia wireless communication systems. Such systems are predicted to provide tremendous improvement in spectrum utilization. In this paper we consider the capacity analysis of Multiple-Input Multiple-Output (MIMO) systems. Space-Time coding schemes are the practical signal design techniques to realize the information theoretic capacity limits of MIMO systems. Here the orthogonal space-time block codes are considered for the capacity and error probability analysis of MIMO systems as a case study. The numerical and simulation results obtained using MATLAB are presented for the Multi-antenna system channel capacity and bit-error probability in Rayleigh fading channels.

On Some Design Issues of Space-Time Coded Multi-Antenna Systems

EURASIP Journal on Advances in Signal Processing, 2002

This paper concerns some design issues and tradeoffs of communication systems equipped with multiple transmit and receive antennas. The general space-time coding/modulation structure by Tarokh et al. (1999) is considered. Several design issues are investigated for this structure. The layered space-time architecture by Foschini (1996) is revisited as a special case of the general structure. It is also used to demonstrate the design and complexity tradeoffs of the system. Through intuitive and analytical explanations, as well as simulations, the design considerations for these space-time transmission structures and their contributions to the performance are shown.

On Limits of Wireless Communications In a Fading Environment When Using Multiple Antennas

Wireless personal communications, 1998

This paper is motivated by the need for fundamental understanding of ultimate limits of bandwidth efficient delivery of higher bit-rates in digital wireless communications and to also begin to look into how these limits might be approached. We examine exploitation of multi-element array (MEA) technology, that is processing the spatial dimension (not just the time dimension) to improve wireless capacities in certain applications. Specifically, we present some basic information theory results that promise great advantages of using MEAs in wireless LANs and building to building wireless communication links. We explore the important case when the channel characteristic is not available at the transmitter but the receiver knows (tracks) the characteristic which is subject to Rayleigh fading. Fixing the overall transmitted power, we express the capacity offered by MEA technology and we see how the capacity scales with increasing SNR for a large but practical number, n, of antenna elements at both transmitter and receiver.

Analysis and performance of some basic space-time architectures (original) (raw)

Related papers