Antonia M. Tulino

Multiple-antenna capacity in the low-power regime

This paper provides analytical characterizations of the impact on the multiple-antenna capacity of several important features that fall outside the standard multiple-antenna model, namely: (i) antenna correlation, (ii) Ricean factors, (iii) polarization diversity, and (iv) out-of-cell interference; all in the regime of low signal-to-noise ratio. The interplay of rate, bandwidth, and power is analyzed in the region of energy per bit close to its minimum value. The analysis yields practical design lessons for arbitrary number of antennas in the transmit and receive arrays.

Capacity of multiple-transmit multiple-receive antenna architectures

The capacity of wireless communication architectures equipped with multiple transmit and receive antennas and impaired by both noise and cochannel interference is studied. We find a closed-form solution for the capacity in the limit of a large number of antennas. This asymptotic solution, which is a sole function of the relative number of transmit and receive antennas and the signal-to-noise and signal-to-interference ratios (SNR and SIR), is then particularized to a number of cases of interest. By verifying that antenna diversity one can substitute for time and/or frequency diversity at providing ergodicity, we show that these asymptotic solutions approximate the ergodic capacity very closely even when the number of antennas is very small.

High-SNR power offset in multiantenna communication

In this paper, the high-SNR multiantenna capacity with coherent receivers on the multiplexing gain, i.e., the multiplicative increase as function of the number of antennas is analyzed. For most channels of interest, such multiplexing gain equals the minimum of the number of transmit and receive antennas. This traditional characterization, however, is unable to quantify the impact of many relevant channel features. As a function of SNR, the capacity is very well approximated, from moderate SNR on, as an affine function. The impact of the various channel features is captured in the power offset (in dB) or zero-order term in the affine expansion.

Capacity of MIMO channels with one-sided correlation

We present closed-form expressions for the marginal density distribution of the unordered eigenvalues of HFH* where F is an input covariance and H is a matrix representing a MIMO (multi-input multi-output) Rayleigh-faded channel with one-sided correlation at either end of the link, transmitter or receiver, with no constraints on the numbers of antennas therein. Using the foregoing distribution, we then derive analytical expressions for the capacity. The expressions found are evaluated through several examples conducted with correlation structures of practical interest.

Asymptotic analysis of improved linear receivers for BPSK-CDMA subject to fading

In this paper, we design and analyze a new class of linear multiuser detectors, which can be applied when the users employ BPSK modulation and the fading coefficients of the active users are known at the receiver (such as base-station demodulation). The tools of asymptotic distribution of the spectrum of large random matrices are used to show that relative to the classical minimum mean-square-error (MMSE) receiver, the output signal-to-noise ratio (SNR) improves by halving the number of effective interferers and adding 3 dB to the input SNR. We also propose sensible approximations to the proposed linear receivers so as to facilitate their use in CDMA systems that employ long codes.

Capacity of antenna arrays with space, polarization and pattern diversity

We present an analytical characterization of multi-antenna capacity in the limit of a large number of antennas. In contrast to previous studies, the entries of the channel matrix are not restricted to be identically distributed, thus incorporating diversity mechanisms that are otherwise excluded, such as those based on the use of antennas with distinct polarizations and radiation patterns. In addition to the capacity, first-order expressions in the low- and high-power regimes are also evaluated both asymptotically and non-asymptotically.

Mercury/waterfilling: optimum power allocation with arbitrary input constellations

For parallel independent Gaussian-noise channels with an aggregate power constraint, independent Gaussian inputs whose powers are allocated according to the waterfilling policy maximize the sum mutual information. In practice, however, discrete signalling constellations such as m-PSK or m-QAM are used in lieu of the ideal Gaussian signals. This paper gives the power allocation policy, referred to as mercury/waterfilling, that maximizes the sum mutual information over parallel channels with arbitrary input constellations

Space-Time Wireless Systems: Multiantenna capacity: myths and realities

Over the last decade, the increases in capacity promised by multiantenna communication techniques have spurred many information-theoretic analyses. Furthermore, information theory has been used as a design tool to optimize the signals fed to the transmit array and to motivate signal processing strategies at the receiver. In this chapter, we catalog a number of misconceptions that have arisen in the multiantenna literature. The focus is on information-theoretic results and their interpretations, rather than on the validity of the various modeling assumptions. After some introductory material, we address several misconceptions about optimum signaling and about the impact of model features, such as antenna correlation, line-of-sight components, and intercell interference. Particular attention is given to the lowand high-power regions. We also briefly touch upon the relationship of the capacity results with some practical transmit and receive architectures. The chapter deals mostly, but not exclusively, with coherent communication.

Theory of Large Dimensional Random Matrices for Engineers

In the last few years, the asymptotic distribution of the singular values of certain random matrices has emerged as a key tool in the analysis and design of wireless communication channels. These channels are characterized by random matrices that admit various statistical descriptions depending on the actual application. The goal of this paper is the investigation and application of random matrix theory with particular emphasis on the asymptotic theorems on the distribution of the squared singular values under various assumption on the joint distribution of the random matrix entries

Asymptotic eigenvalue moments for linear multiuser detection

Using the theory of lattices of non-crossing partitions, an explicit expression is obtained for the asymptotic moments of certain infinite random matrices that arise in multiuser detection in DS-CDMA systems with random spreading. By using this explicit expression, we obtain a self-contained proof of the Tse-Hanly formula for the output signal-to-interference-plus-noise ratio of a MMSE multiuser detector. The asymptotic moment results are used to design a low-complexity polynomial approximation of a linear multiuser detector. Analytical and numerical results of their performance analysis are also given.