On the Impact of Antenna Topologies for Massive MIMO Systems

Approximate expressions for the spatial correlation of cylindrical and uniform rectangular arrays (URA) are derived using measured distributions of angles of departure (AOD) for both the azimuth and zenith domains. We examine massive multiple-input-multiple-output (MIMO) convergence properties of the correlated channels by considering a number of convergence metrics. The per-user matched filter (MF) signal-to-interference-plus-noise ratio (SINR) performance and convergence rate, to respective limiting values, of the two antenna topologies is also explored.Comment: 6 pages, 6 figure

Interference and Deployment Issues for Cognitive Radio Systems in Shadowing Environments

In this paper we describe a model for calculating the aggregate interference encountered by primary receivers in the presence of randomly placed cognitive radios (CRs). We show that incorporating the impact of distance attenuation and lognormal fading on each constituent interferer in the aggregate, leads to a composite interference that cannot be satisfactorily modeled by a lognormal. Using the interference statistics we determine a number of key parameters needed for the deployment of CRs. Examples of these are the exclusion zone radius, needed to protect the primary receiver under different types of fading environments and acceptable interference levels, and the numbers of CRs that can be deployed. We further show that if the CRs have apriori knowledge of the radio environment map (REM), then a much larger number of CRs can be deployed especially in a high density environment. Given REM information, we also look at the CR numbers achieved by two different types of techniques to process the scheduling information.Comment: to be presented at IEEE ICC 2009. This posting is the same as the original one. Only author's list is updated that was unfortunately not correctly mentioned in first versio

On the Convergence of Massive MIMO Systems

In this paper we examine convergence properties of massive MIMO systems with the aim of determining the number of antennas required for massive MIMO gains. We consider three characteristics of a channel matrix and study their asymptotic behaviour. Furthermore, we derive ZF SNR and MF SINR for a scenario of unequal receive powers. In our results we include the effects of spatial correlation. We show that the rate of convergence of channel metrics is much slower than that of the ZF/MF precoder properties.Comment: 6 pages, 6 figures, ICC 201

Hybrid Warfare: The Struggle of Military Forces to Adapt to Complex Opponents

Streaming video requires RealPlayer to view.The University Archives has determined that this item is of continuing value to OSU's history.Hybrid warfare, a combination of conventional and irregular forces fighting against a common foe, has been an integral part of the historical landscape since the ancient world, but these conflicts have only recently been categorized as a unique type of conflict. Informed defense analysts believe that hybrid wars are the most likely conflicts in the 21st century. An historical examination of hybrid wars will help to illuminate the various aspects of these conflicts, how great powers have dealt with them, and potential prospects for the future of these types of wars. The United States is currently engaged in extended counterinsurgency conflicts in Iraq and Afghanistan and has significant military and other national assets assisting other states and regions against insurgencies. Rather than historical anomalies, Iraq and Afghanistan are harbingers of the wars to come in the next several decades. Nation state competitors are unlikely to challenge the United States in the realm of high-technology, conventional warfare. Rather, they will likely use a combination of conventional and insurgent/guerrilla forces – hybrid forces – to wear down American military capabilities in extended campaigns of exhaustion. The United States and its allies must study and understand the strategic, operational, tactical, and doctrinal parameters of hybrid conflicts and prepare to apply lessons from them. This project, which will illuminate historical examples of hybrid warfare from Ancient Greece to the modern world, is a step along that journey of understanding.Ohio State University. Mershon Center for International Security StudiesEvent Web page, streaming video, event photos, event poste

ANALYSIS OF THE MUTUAL TRADE BETWEEN THE EU AND INDONESIA

Mutual trade between EU countries and Indonesia is a bilateral commodity trade flow exceeding 17 billion Euros. Analysis of the trade between the two entities is an important contribution leading to the definition of the significance that the ongoing cooperation between the EU and Indonesia has. EU is for Indonesia very important trading partner, for EU is Indonesia a strategic political partner. The bilateral trade is currently greatly benefiting Indonesia, however, this market has a potential for EU due to the fact, that it is one of the most populous country in the Asian region and the in world in general. The trade exchange is based on export and import of most basic aggregate commodities; while between the two partners exist significant differences in terms of available comparative advantages. A specificity of the mutual trade is the limited territorial structure of this exchange, as the main volume of transactions is realized between Indonesia and only a few EU countries.   Keywords: EU, Indonesia, mutual, foreign trade, commodity, territory, structure, analysis, competitivenes

Performance of Cognitive Radio Systems with Imperfect Radio Environment Map Information

In this paper we describe the effect of imperfections in the radio environment map (REM) information on the performance of cognitive radio (CR) systems. Via simulations we explore the relationship between the required precision of the REM and various channel/system properties. For example, the degree of spatial correlation in the shadow fading is a key factor as is the interference constraint employed by the primary user. Based on the CR interferers obtained from the simulations, we characterize the temporal behavior of such systems by computing the level crossing rates (LCRs) of the cumulative interference represented by these CRs. This evaluates the effect of short term fluctuations above acceptable interference levels due to the fast fading. We derive analytical formulae for the LCRs in Rayleigh and Rician fast fading conditions. The analytical results are verified by Monte Carlo simulations.Comment: presented at IEEE AusCTW 2009. Journal versions are under preparation. This posting is the same as the original one. Only author's list is updated that was unfortunately not correctly mentioned in the first versio

Channel Capacity Limits of Cognitive Radio in Asymmetric Fading Environments

Cognitive radio technology is an innovative radio design concept which aims to increase spectrum utilization by exploiting unused spectrum in dynamically changing environments. By extending previous results, we investigate the capacity gains achievable with this dynamic spectrum approach in asymmetric fading channels. More specifically, we allow the secondary-to-primary and secondary-to-secondary user channels to undergo Rayleigh or Rician fading, with arbitrary link power. In order to compute the capacity, we derive the distributions of ratios of Rayleigh and Rician variables. Compared to the symmetric fading scenario, our results indicate several interesting features of the capacity behaviour under both average and peak received power constraints. Finally, the impact of multiple primary users on the capacity under asymmetric fading has also been studied.Comment: 6 pages, 8 figures, in Proceedings of IEEE International Conference on Communications (ICC 2008), Beijing, China, May 19-23, 200