Alenka G. Zajic

Wideband MIMO Mobile-to-Mobile Channels: Geometry-Based Statistical Modeling With Experimental Verification

A 3-D reference model for wideband multiple-input multiple-output (MIMO) mobile-to-mobile (M-to-M) channels is reviewed along with its corresponding first- and second-order channel statistics. To validate the reference model, an experimental MIMO M-to-M channel-sounding campaign was conducted for M-to-M vehicular communication with vehicles that travel along surface streets and expressways in a metropolitan area. To compare the first- and second-order channel statistics that were obtained from the reference model with those obtained from the empirical measurements, a new maximum-likelihood-based stochastic estimator is derived to extract the relevant model parameters from the measured data. The measured data is processed and compared with the analytical results. The close agreement between the analytically and empirically obtained channel statistics confirms the utility of the proposed reference model and the method for estimating the model parameters.

Space-Time Correlated Mobile-to-Mobile Channels: Modelling and Simulation

A single- and double-bounced two-ring parametric reference model is proposed for multiple-input multiple-output (MIMO) mobile-to-mobile (M-to-M) Ricean fading channels. From this model, a closed-form joint space-time correlation function and a space-Doppler power spectrum are derived for a two-dimensional (2D) non-isotropic scattering environment. Also, space-time correlation functions for the in-phase and quadrature components of the complex faded envelope are derived, assuming a 2D isotropic scattering environment. Finally, two new sum-of-sinusoids based simulation models for MIMO M-to-M Ricean fading channels are proposed. The statistics of the simulation models are verified by simulation. The results show that the simulation models are a good approximation of the reference model and that they outperform existing simulation models.

Three-Dimensional Modeling, Simulation, and Capacity Analysis of Space–Time Correlated Mobile-to-Mobile Channels

A 3-D reference model is proposed for multiple-input multiple-output (MIMO) mobile-to-mobile (M-to-M) multipath-fading channels. From this model, a closed-form joint space-time correlation function is derived for a 3-D nonisotropic scattering environment. Two sum-of-sinusoids-based 3-D simulation models for MIMO M-to-M multipath-fading channels are proposed. The statistics of the simulation models are verified by simulation. Finally, these simulation models are used to evaluate the effect of the space-time correlation on the outage capacity of uniform linear antenna arrays and to compare the capacities of linear, circular, and spherical antenna arrays.

Three-dimensional modeling and simulation of wideband MIMO mobile-to-mobile channels

A three-dimensional (3-D) geometrical propagation model for wideband multiple-input multiple-output (MIMO) mobile-to-mobile (M-to-M) communications is proposed. Based on the geometrical model, a 3-D parametric reference model for wideband MIMO M-to-M multipath fading channels is developed. From the reference model, the corresponding space-time-frequency correlation function is derived for a 3-D non-isotropic scattering environment. It is shown that the time and frequency dispersion of a wide sense stationary uncorrelated scattering channel cannot be treated independently, contrary to common practice. From the space-time-frequency correlation function, the space-Doppler power spectral density and the power space-delay spectrum are derived and compared with measured data. Finally, a new sum-of-sinusoids based simulation model for wideband MIMO M-to-M Ricean fading channels is proposed. The statistics of the simulation model are verified by simulation. The results show that the simulation model is a good approximation of the reference model.

A new simulation model for mobile-to-mobile Rayleigh fading channels

A new statistical sum-of-sinusoids simulation model is proposed for mobile-to-mobile Rayleigh fading channels and compared with existing simulation models. The new proposed model has a lower variance of the auto-correlation functions, i.e., it converges faster and has a lower correlation between the in-phase and quadrature components of the complex faded envelope than existing simulation models. This model yields adequate statistics with only 30 simulation runs

Enhancing the gain of helical antennas by shaping the ground conductor

We have observed that the size and shape of the ground conductor of axial mode helical antennas have significant impact on the antenna gain. By shaping the ground conductor, we have increased the gain of a helical antenna for as much as 4 dB. Theoretical results are verified by measurements.

Experimental Demonstration of Electromagnetic Information Leakage From Modern Processor-Memory Systems

This paper shows that electromagnetic (EM) information leakage from modern laptops and desktops (with no peripherals attached) is indeed possible and is relatively easy to achieve. The experiments are performed on three laptop systems and one desktop system with different processors (Intel Centrino, Core 2, Core i7, and AMD Turion), and show that both active (program deliberately tries to cause emanations at a particular frequency) and passive (emanations at different frequencies happen as a result of system activity) EM side-channel attacks are possible on all the systems we tested. Furthermore, this paper shows that EM information leakage can reliably be received at distances that vary from tens of centimeters to several meters including the signals that have propagated through cubicle or structural walls. Finally, this paper shows how activity levels and data values used in accessing different parts of the memory subsystem (off-chip memory and each level of on-chip caches) affect the transmission distance.

A Three-Dimensional MIMO Mobile-to-Mobile Channel Model

A three-dimensional (3-D) geometrical propagation model for multi-input-multi-output (MIMO) mobile-to-mobile (M-to-M) communications is proposed. Based on the geometrical model, a 3-D reference model for MIMO M-to-M multipath fading channels is proposed. From the reference model, a closed-form joint space-time correlation function is derived for a 3-D non-isotropic scattering environment and it is show that many existing correlation functions are special cases of the derived space-time correlation function.

A Practical Methodology for Measuring the Side-Channel Signal Available to the Attacker for Instruction-Level Events

This paper presents a new metric, which we call Signal Available to Attacker (SAVAT), that measures the side channel signal created by a specific single-instruction difference in program execution, i.e. The amount of signal made available to a potential attacker who wishes to decide whether the program has executed instruction/event A or instruction/event B. We also devise a practical methodology for measuring SAVAT in real systems using only user-level access permissions and common measurement equipment. Finally, we perform a case study where we measure electromagnetic (EM) emanations SAVAT among 11 different instructions for three different laptop systems. Our findings from these experiments confirm key intuitive expectations, e.g. That SAVAT between on-chip instructions and off-chip memory accesses tends to be higher than between two on-chip instructions. However, we find that particular instructions, such as integer divide, have much higher SAVAT than other instructions in the same general category (integer arithmetic), and that last-level-cache hits and misses have similar (high) SAVAT. Overall, we confirm that our new metric and methodology can help discover the most vulnerable aspects of a processor architecture or a program, and thus inform decision-making about how to best manage the overall side channel vulnerability of a processor, a program, or a system.

Statistical Modeling of MIMO Mobile-to-Mobile Underwater Channels

This paper proposes a geometry-based statistical model for wideband multiple-input-multiple-output (MIMO) mobile-to-mobile (M-to-M) shallow-water acoustic (SWA) multipath fading channels. Based on the reference model, the corresponding MIMO time-frequency correlation function, Doppler power spectral density, and delay cross-power spectral density are derived. These statistics are important tools for the design and performance analysis of MIMO M-to-M SWA communication and sonar systems. Finally, the derived statistics are compared with the experimentally obtained channel statistics, and close agreement is observed.