5G green cellular networks considering power allocation schemes

It is important to assess the effect of transmit power allocation schemes on the energy consumption on random cellular networks. The energy efficiency of 5G green cellular networks with average and water-filling power allocation schemes is studied in this paper. Based on the proposed interference and achievable rate model, an energy efficiency model is proposed for MIMO random cellular networks. Furthermore, the energy efficiency with average and water-filling power allocation schemes are presented, respectively. Numerical results indicate that the maximum limits of energy efficiency are always there for MIMO random cellular networks with different intensity ratios of mobile stations (MSs) to base stations (BSs) and channel conditions. Compared with the average power allocation scheme, the water-filling scheme is shown to improve the energy efficiency of MIMO random cellular networks when channel state information (CSI) is attainable for both transmitters and receivers.Comment: 14 pages, 7 figure

Game theoretic aspects of distributed spectral coordination with application to DSL networks

In this paper we use game theoretic techniques to study the value of cooperation in distributed spectrum management problems. We show that the celebrated iterative water-filling algorithm is subject to the prisoner's dilemma and therefore can lead to severe degradation of the achievable rate region in an interference channel environment. We also provide thorough analysis of a simple two bands near-far situation where we are able to provide closed form tight bounds on the rate region of both fixed margin iterative water filling (FM-IWF) and dynamic frequency division multiplexing (DFDM) methods. This is the only case where such analytic expressions are known and all previous studies included only simulated results of the rate region. We then propose an alternative algorithm that alleviates some of the drawbacks of the IWF algorithm in near-far scenarios relevant to DSL access networks. We also provide experimental analysis based on measured DSL channels of both algorithms as well as the centralized optimum spectrum management

Material Limitations on the Detection Limit in Refractometry

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min{Dn} > eta with n+i*eta being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because silicon absorbs strongly.Comment: Published in Special Issue "Laser Spectroscopy and Sensing", Edited by Prof. M.W. Sigris

Elastocapillary filling of deformable nanochannels

The capillary filling speed of wetting liquids of varying viscosity and surface tension in hydrophilic nanochannels with an elastic capping layer has been analyzed. The channels, with a height just below 80 nm, are suspended by a thin flexible membrane that easily deforms due to the negative pressure which develops behind the moving meniscus. In the elastocapillary filling of the channels, two opposite effects compete: the decreased cross channel sections increase the flow resistance, while the Laplace pressure that acts as the driving force becomes more negative due to the increased meniscus curvature. Although the meniscus position shows a square root of time behavior as described by the Washburn relation, the net result of the induced bending of the membranes is a definite increase of the filling speed. We propose a relatively straightforward model for this elastocapillary process and present experimental results of the filling speed of ethanol, water, cyclohexane and acetone that are found to be in good agreement with the presented model, for membrane deflections of up to 80 percent of the original channel height