52 research outputs found

    From Multi-Keyholes to Measure of Correlation and Power Imbalance in MIMO Channels: Outage Capacity Analysis

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    An information-theoretic analysis of a multi-keyhole channel, which includes a number of statistically independent keyholes with possibly different correlation matrices, is given. When the number of keyholes or/and the number of Tx/Rx antennas is large, there is an equivalent Rayleigh-fading channel such that the outage capacities of both channels are asymptotically equal. In the case of a large number of antennas and for a broad class of fading distributions, the instantaneous capacity is shown to be asymptotically Gaussian in distribution, and compact, closed-form expressions for the mean and variance are given. Motivated by the asymptotic analysis, a simple, full-ordering scalar measure of spatial correlation and power imbalance in MIMO channels is introduced, which quantifies the negative impact of these two factors on the outage capacity in a simple and well-tractable way. It does not require the eigenvalue decomposition, and has the full-ordering property. The size-asymptotic results are used to prove Telatar's conjecture for semi-correlated multi-keyhole and Rayleigh channels. Since the keyhole channel model approximates well the relay channel in the amplify-and-forward mode in certain scenarios, these results also apply to the latterComment: accepted by IEEE IT Trans., 201

    Capacity and performance analysis of advanced multiple antenna communication systems

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    Multiple-input multiple-output (MIMO) antenna systems have been shown to be able to substantially increase date rate and improve reliability without extra spectrum and power resources. The increasing popularity and enormous prospect of MIMO technology calls for a better understanding of the performance of MIMO systems operating over practical environments. Motivated by this, this thesis provides an analytical characterization of the capacity and performance of advanced MIMO antenna systems. First, the ergodic capacity of MIMO Nakagami-m fading channels is investigated. A unified way of deriving ergodic capacity bounds is developed under the majorization theory framework. The key idea is to study the ergodic capacity through the distribution of the diagonal elements of the quadratic channel HHy which is relatively easy to handle, avoiding the need of the eigenvalue distribution of the channel matrix which is extremely difficult to obtain. The proposed method is first applied on the conventional point-to-point MIMO systems under Nakagami-m fading, and later extended to the more general distributed MIMO systems. Second, the ergodic capacity of MIMO multi-keyhole and MIMO amplify-and-forward (AF) dual-hop systems is studied. A set of new statistical properties involving product of random complex Gaussian matrix, i.e., probability density function (p.d.f.) of an unordered eigenvalue, p.d.f. of the maximum eigenvalue, expected determinant and log-determinant, is derived. Based on these, analytical closedform expressions for the ergodic capacity of the systems are obtained and the connection between the product channels and conventional point-to-point MIMO channels is also revealed. Finally, the effect of co-channel interference is investigated. First, the performance of optimum combining (OC) systems operating in Rayleigh-product channels is analyzed based on novel closed-form expression of the cumulative distribution function (c.d.f.) of the maximum eigenvalue of the resultant channel matrix. Then, for MIMO Rician channels and MIMO Rayleigh-product channels, the ergodic capacity at low signal-to-noise ratio (SNR) regime is studied, and the impact of various system parameters, such as transmit and receive antenna number, Rician factor, channel mean matrix and interference-tonoise- ratio, is examined

    MIMO Channel Modelling for Satellite Communications

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    Information-theoretic Characterization of MIMO Systems with Multiple Rayleigh Scattering

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    We present an information-theoretic analysis of a point-to-point Multiple-Input-Multiple-Output(MIMO) link affected by Rayleigh fading and multiple scattering, under perfect channel state informationat the receiver. Unlike previous work addressing this setting, we investigate the Random Coding ErrorExponent, its associated cutoff rate and the Expurgated Error Exponent, and derive closed-form expres-sions for them. Moreover, leveraging the average mutual information expression presented in [1], wederive another important metric, namely, the sum rate, under linear receive processing and independentstream decoding. In particular, we characterize the performance of the Minimum Mean Squared Errorreceiver in closed form, and that of the Zero Forcing receiver by resorting to bounding techniques. Thebulk of the work relies on results about finite-dimensional random matrix products, a number of whichare novel and detailed in the Appendices. The analysis, validated through numerical results, highlightsthe severe degradation in the performance of linear receivers due to multi-fold scattering. It also unveilsthe performance trend of multiple scattering MIMO channels as a function of the number of antennasand the number of scattering stages

    Relay technology for performance improvement in WiMAX system

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    Analysis of multiuser MIMO downlink networks using linear transmitter and receivers

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    In contrast to dirty-paper coding (DPC) which is largely information theoretic, this paper proposes a linear codec that can spatially multiplex the multiuser signals to realize the rich capacity of multiple-input multiple-output (MIMO) downlink broadcast (point-to-multipoint) channels when channel state information (CSI) is available at the transmitter. Assuming single-stream (or single-mode) communication for each user, we develop an iterative algorithm, which is stepwise optimal, to obtain the multiuser antenna weights accomplishing orthogonal space-division multiplexing (OSDM). The steady state solution has a straightforward interpretation and requires only maximal-ratio combiners (MRC) at the mobile stations to capture the optimized spatial modes. Our main contribution is that the proposed scheme can greatly reduce the processing complexity (at least by a factor of the number of base station antennas) while maintaining the same error performance when compared to a recently published OSDM method. Intensive computer simulations show that the proposed scheme promises to provide multiuser diversity in addition to user separation in the spatial domain so that both diversity and multiplexing can be obtained at the same time for multiuser scenario. © 2004 Hindawi Publishing Corporation.published_or_final_versio

    Information-theoretic analysis of MIMO channel sounding

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    The large majority of commercially available multiple-input multiple-output (MIMO) radio channel measurement devices (sounders) is based on time-division multiplexed switching (TDMS) of a single transmit/receive radio-frequency chain into the elements of a transmit/receive antenna array. While being cost-effective, such a solution can cause significant measurement errors due to phase noise and frequency offset in the local oscillators. In this paper, we systematically analyze the resulting errors and show that, in practice, overestimation of channel capacity by several hundred percent can occur. Overestimation is caused by phase noise (and to a lesser extent frequency offset) leading to an increase of the MIMO channel rank. Our analysis furthermore reveals that the impact of phase errors is, in general, most pronounced if the physical channel has low rank (typical for line-of-sight or poor scattering scenarios). The extreme case of a rank-1 physical channel is analyzed in detail. Finally, we present measurement results obtained from a commercially employed TDMS-based MIMO channel sounder. In the light of the findings of this paper, the results obtained through MIMO channel measurement campaigns using TDMS-based channel sounders should be interpreted with great care.Comment: 99 pages, 14 figures, submitted to IEEE Transactions on Information Theor
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