Modelling the energy efficiency of microcell base stations

The power consumption of wireless access networks will become a major issue in the coming years. Therefore, it is important to have a realistic idea about the power consumption of each element in those access networks. In this paper, an energy efficiency model for microcell base stations is proposed. Based on this model, the energy efficiency of microcell base stations is compared for various wireless technologies, namely mobile WiMAX, HSPA and LTE. The power consumption of microcell base stations is about 70-77% lower than for macrocell base stations but a macrocell base station is more energy-efficient than a microcell base station for the same bit rates. However, for the considered case and assuming our parameters are correct, a reduction in power consumption can be obtained by using microcell base stations to fill coverage holes

Evaluation of performance of mobile terminal antennas

Fast development of new mobile communications equipment results in demand for fast and reliable evaluation methods to estimate the performance of mobile terminals because the performance of antennas located on the terminals varies in different multipath propagation environments. Two methods presented in this thesis provide new possibilities in antenna design because, from now on, the performance of new antennas can be tested already before a prototype antenna is constructed by using existing radio channel libraries and simulated radiation patterns of the antennas. The performance can be estimated by calculating the mean effective gain (MEG) of the antenna using the elevation power distribution or by a plane wave -based method using sets of incident plane waves and the radiation pattern of an antenna. In addition to different propagation environments, the effects of the user on performance can be included in the evaluation. In this thesis, estimating the MEG of different antennas using the elevation power distribution and the power patterns of the antennas is shown to be an accurate and fast method by comparing the results with direct radio channel measurements. The mean difference between the methods is −0.18 dB with standard deviation of 0.19 dB. The usefulness of the evaluation method is demonstrated by evaluating the performance of several antennas located on mobile terminals. The antenna evaluation provided important and unique knowledge of the effect of both the environment and the user on performance. Because in calculating the radiation efficiency of the antenna we assume uniform incident field, the efficiency can result in a performance estimation that does not correspond to real usage situations. Therefore, including the environmental effects in the evaluation procedure is important, although the effect of the antenna is more important than the effect of the environment on MEG. It was noticed with calculated Gaussian-shaped beams that tilting or changing the beamwidth of a mobile terminal antenna has an effect of about 2 dB on MEG in multipath environments. Matching the polarization of the antenna to that of the environment can improve the performance more. A novel incident plane wave -based tool has been developed for evaluating the performance of antenna configurations designed for diversity and Multiple-Input Multiple-Output (MIMO) systems. In this thesis, the instantaneous joint contribution of incident field consisting of a number of extracted plane waves and the complex three-dimensional radiation pattern of the antenna is shown to be accurate and extremely fast way to estimate the diversity advantages of different antenna configurations in time-variable radio channels. The difference between the diversity gains achieved by the plane wave -based method and by the direct radio channel measurements is on average less than 0.9 dB. Moreover, the radio channel can be exactly the same for all antenna configurations under test. Furthermore, this thesis includes evaluation of the performance of different MIMO antenna configurations. The studied antenna configurations have been selected from the 16×64 MIMO channel measurement data. A novel way of using one omnidirectional reference antenna in a normalization procedure is shown to be reasonable especially in cases of antenna arrays consisting of directive elements. Three different propagation environments are used as evaluation platforms. The azimuth orientation of mobile terminal antennas may influence the performance of a MIMO antenna configuration significantly. In MIMO configurations compact dual-polarized receiving antennas provide capacity performance almost equal to the arrays employing single polarization.reviewe

From Susa to Sippar: the travels of two bulls, a mountain and a tree

Among the Old Babylonian seals of Sippar there is one that appears to be unique. In this study we try to find out whether the motif on this seal was attested elsewhere during the Old Babylonian period and whether it already existed during previous periods. First, we determine the iconographic position of the motif by comparing it to similar ones. Then, by describing the motif’s journey through space and time, we argue that its origin lies in the ancient city of Susa. Finally, we look at the motif’s absence during the Old Babylonian period and link the presence of the motif on a Sippar seal to the fact that it belonged to a Sippar merchant

Multi-element antenna for DVB-H terminal

Tässä diplomityössä tutkittiin monielementtiantennien käyttökelpoisuutta kannettavissa Digital Video Broadcasting – Handheld (DVB-H)-digitaalitelevisiovastaanottimissa. Työssä suunniteltiin ja valmistettiin kaksielementtiantenni DVB-H-käyttöön. Antennin toimintaa arvioitiin simuloinneilla ja mittauksilla. Monielementtiantennijärjestelmien, kuten multiple-input multiple-output (MIMO), käyttö mahdollistaa radiotietoliikenneyhteyden kapasiteetin kasvun tai niillä voidaan lisätä yhteyden luotettavuutta verrattuna perinteiseen yhden vastaanotin- ja lähetysantennin järjestemään. MIMO-järjestelmän haittapuolena voidaan pitää lähettimen ja vastaanottimen rakenteen monimutkaistumista. DVB-H-signaalin vastaanotto tapahtuu matalalla taajuudella ja leveällä taajuuskaistalla (noin. 470 – 800 MHz), mikä tekee pienen laitteen antennisuunnittelusta haastavaa. Kannettavan TV-vastaanottimen sisäisistä antenneista tulee väistämättä sähköisesti pieniä ja laajakaistaista toimintaa on vaikea saavuttaa. Lisäksi nykyaikaisessa kannettavassa päätelaitteessa on hyvin rajallinen määrä paikkoja, joihin DVB-H-antennit voidaan sijoittaa. Matalasta taajuudesta ja laitteen pienestä koosta johtuen korreloimattomia antennielementtejä on vaikea toteuttaa. Tässä työssä antennit toteutettiin kytkentäelementteihin perustuvalla antennirakenteella, jossa antenni viritetään resonanssiin sovituspiirin avulla. Eri antennirakenteilla ja elementtien sijoittelulla saavutettavia kaistanleveyksiä sekä verhokäyrä-korrelaatioita tutkittiin aluksi simuloinneilla. Lopulta päädyttiin käyttämään kahta antennielementtiä, jotka asetettiin päätelaitteen piirilevyä kuvaavan maatason nurkkiin samalle lyhyelle sivulle. Työssä suunniteltiin kapeakaistainen yksiresonanssisovituspiiri mittauksia varten, sekä leveäkaistainen kaksoisresonanssisovituspiiri kattamaan koko DVB-H-taajuuskaista. Koska antennirakenteesta haluttiin pieni, jouduttiin DVB-H-kaista jakamaan kahteen osaan ja suunnittelemaan sovituspiirit erikseen molemmille osakaistoille. Lopullisessa antennissa haluttu sovituspiiri valittaisiin RF-kytkimillä. Tällä menettelyllä DVB-H-antenneille asetettu toteutuneen vahvistuksen spesifikaatio ylitettiin 2.5 dB:n marginaalilla sekä simuloinneissa että mittauksissa. Antennirakenteen MIMO-toimintaa tutkittiin measurement based antenna testbed (MEBAT)-nimisellä antennievaluaatiotyökalulla. MEBAT:in avulla kaksielementtiantennin toimintaa voitiin simuloida realistisessa etenemisympäristöissä. Simulointeja varten suunniteltiin yksielementtinen referenssiantenni, jotta voitiin selvittää, onko useamman elementin käytöstä hyötyä. Simulointituloksista ilmenee, että suurin hyöty kaksielementtiantennin käytöstä saavutetaan suurilla luotettavuustasoilla. Tällöin käyttämällä 2 x 2 MIMO-järjestelmää keskinäisinformaatio voi olla noin kaksin-nelinkertainen verrattuna single-input single-output (SISO)-konfiguraatioon. Matalammilla luotettavuustasoilla ero on pienempi. MIMO-järjestelmän suorituskykyyn vaikuttavat käyttöympäristön lisäksi myös vastaanottoantennin asento sekä lähetysantennissa käytettävät polarisaatiot. Myös näitä asioita tutkittiin MEBAT-simuloinneilla.In this thesis feasibility to implement multi-element antenna configurations in handheld digital television receivers (Digital Video Broadcasting – Handheld (DVB-H)) has been studied. A two-element antenna for a DVB-H terminal was designed, manufactured and the performance of the antenna was evaluated with simulations and measurements. The use of multi-element antenna systems such as multiple-input multiple-output (MIMO) can enhance the mutual information or reliability of the wireless communications link compared to a single-element antenna system. The drawback of using the MIMO system is the increased complexity of the transceiver. The DVB-H system works at about 470 – 800 MHz frequency range and the relative bandwidth is very broad. This makes antenna designing challenging because an internal antenna in a handheld terminal is inevitably electrically small and broad bandwidth is difficult to achieve. In addition, in a handheld terminal there are very few places where DVB-H antennas can be located. Due to low frequency and small size of the terminal it is difficult to implement uncorrelated antenna elements. In this work antenna elements were realized with a coupling element based antenna structure. These antennas are tuned to resonance with a matching circuit. At first achievable bandwidths and envelope correlation coefficients of different antenna element structures and their locations were investigated with simulations. Finally, the multi-element antenna was implemented with two antenna elements which were located in the corners of the ground plane at the same short side. The ground plane represents the circuit board of the terminal. In this thesis a narrow-band single-resonant matching circuit was designed to evaluate the performance of the antenna with measurements and a broad-band dual-resonant matching circuit to cover the whole DVB-H band. Because the size of the antenna structure was desired to be small, the DVB-H band was divided into two parts and separate matching circuits were designed for both sub-bands. In the final antenna the desired matching circuit would be selected with RF switches. With this procedure, the realized gain specification of the DVB-H antennas was fulfilled with a 2.5 dB margin in simulations and measurements. The MIMO performance of the dual-element antenna structure was evaluated in realistic propagation environments with an antenna analysis tool called measurement based antenna testbed (MEBAT). A single-element reference antenna was designed for the MEBAT simulations in order to gain knowledge whether it is useful to have several antenna elements in a DVB-H receiver. According to simulation results, the greatest benefit from the use of the dual-element antenna is attained at high reliability levels. In that case the mutual information of a 2 x 2 MIMO system can be two to four times higher than with a single-input single-output (SISO) configuration. At lower reliability level the difference is smaller. The performance of the MIMO system does not depend only on the signal environment but also on the orientation of the receiving antenna and on the polarizations of the transmitting antennas. These matters were also investigated with MEBAT simulations

Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks

Conventional cellular wireless networks were designed with the purpose of providing high throughput for the user and high capacity for the service provider, without any provisions of energy efficiency. As a result, these networks have an enormous Carbon footprint. In this paper, we describe the sources of the inefficiencies in such networks. First we present results of the studies on how much Carbon footprint such networks generate. We also discuss how much more mobile traffic is expected to increase so that this Carbon footprint will even increase tremendously more. We then discuss specific sources of inefficiency and potential sources of improvement at the physical layer as well as at higher layers of the communication protocol hierarchy. In particular, considering that most of the energy inefficiency in cellular wireless networks is at the base stations, we discuss multi-tier networks and point to the potential of exploiting mobility patterns in order to use base station energy judiciously. We then investigate potential methods to reduce this inefficiency and quantify their individual contributions. By a consideration of the combination of all potential gains, we conclude that an improvement in energy consumption in cellular wireless networks by two orders of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843