Goran Petrović

Measurements and Modelling of Base Station Power Consumption under Real Traffic Loads

Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient.

On interdependence among transmit and consumed power of macro base station technologies

Dynamic adaptation of the base stations on/off activity or transmit power, according to space and time traffic variations, are measures accepted in the most contemporary resource management approaches dedicated to improving energy efficiency of cellular access networks. Practical implementation of both measures results in changes to instantaneous base station power consumption. In this paper, extensive analyses presenting influence of the transmit power scaling and on/off switching on instantaneous macro base stations power consumption are given. Based on real on-site measurements performed on a set of macro base stations of different access technologies and production years, we developed linear power consumption models. These models are developed by means of linear regression and precisely model the influence of transmit power on instantaneous power consumption for the second, third and fourth generations of macro base stations. In order to estimate the potential energy savings of transmit power scaling and on/off switching for base stations of different generations, statistical analyses of measured power consumptions are performed. Also, transient times and variations of base stations instantaneous power consumption during transient periods initiated with on/off switching and transmit power scaling are presented. Since the developed power consumption models have huge confidence follow measured results, they can be used as general models for expressing the relationship between transmitted and consumed power for macro base stations of different technologies and generations.

Detection of broken rotor bar in squirrel-cage induction machines using stator zero-components

In this paper a method for the broken rotor bar fault detection of induction squirrel cage machines is presented. This method is based on measurements and frequency analysis of the sum of the stator phase currents (the stator circular current) for delta connected windings. For the case of the star connected windings the stator neutral point voltage is measured and analyzed. A model of squirrel cage induction machine, which takes into account the stator windings and rotor cage layout, is used for theoretical investigations of the proposed method. Based on the theoretical investigations it has been found out that the spectrum of the stator circular current, and also the neutral point voltage, contains the rotor fault-related interharmonics. At the same time, these interharmonics are the largest components in the frequency spectrum. The proposed method has been experimentally verified and compared with the procedure based on the frequency analysis of the line current.

Method for nonlinear fitting and impedance analysis with LCR meter

In this paper new method for nonlinear fitting application is defined, described and tested. The method used the data acquired with LCR meter, nonlinear models of equivalent circuits, nonlinear fitting algorithm and iterative procedure for minimization mean square error between input data and nonlinear impedance model. The low cost LCR meter has been used and adopted to perform frequency range sweep impedance analysis and substitute more expensive impedance analyzer instruments. The method is tested in laboratory with different RLC circuit structures. Presented method for nonlinear fitting and impedance analysis can be applied on data acquired with different instruments according to application needs.