Cell Phone Signals Research Articles

Inferring travel from social media

Introduction The spread of infectious diseases is facilitated by human travel. Disease is often introduced by travelers and then spread among susceptible individuals. Likewise, uninfected susceptible travelers can move into populations sustaining the spread of an infectious disease. Several disease-modeling efforts have incorporated travel and census data in an effort to better understand the spread of disease. Unfortunately, most travel data are not fine grained enough to capture individual movements over long periods and large spaces. Alternative methods (e.g., tracking currency movements or cell phone signals) have been suggested to measure how people move with higher resolution but these are often sparse, expensive and not readily available to researchers. FourSquare is a social media application that permits users to ‘check-in’ (i.e., record their currentlocation at stores, restaurants, etc.) via their mobile telephones in exchange for incentives (e.g., location-specific coupons). FourSquare and similar applications (Gowalla, Yelp, etc.) generally broadcast each check-in via Twitter or Facebook; in addition, some GPS-enabled mobile Twitter clients add explicit geocodes to individual tweets. Here, we propose the use of geocoded social media data as a real-time fine-grained proxy for human travel.

Looking for radio waves with a simple radio wave detector

I created a simple device that can detect radio waves in a classroom. In physics classes I tell students that we live in a sea of radio waves. They come from TV, radio, and cell phone signals as well as other sources. Students don't realize this because those electromagnetic waves are invisible. So, I wondered if I could come up with a way to detect the waves and help students to understand them better. Electromagnetic wave meters, which measure intensity of radio waves quantitatively, are commercially available. However, to students most of these are black boxes, and at the introductory level it is more effective to detect radio waves in a simpler way. This paper describes my device and how I have used it in my classes.

AFTERWORD

AFTERWORD Mobile money, money magic, purse limits and pins: tracing monetary pragmatics Bill Maurer [W]e know no system that functions perfectly, that is to say, without losses, flights, wear and tear, errors, accidents, opacity a system whose return is one for one. (Michel Serres, The Parasite) Purse limits. They come up from time to time as I conduct interviews with people involved in the emerging field of mobile phone-enabled money transfer and savings services ‘mobile money’, as many inside the industry call it. A purse limit is a regulatory construct. It is the maximum amount of electronic value that can be stored in a stand- alone electronic device or in a virtual account linked to a phone number, without requiring verification of the identity of the person who owns that value. Although promoters of mobile money announce that the service will lead to the demise of cash, purse limits, as we shall see, are intimately intertwined with the materiality of the banknote. And though historically populists and other critics castigated paper money for its insubstantiality and fictionality, in the current moment cash comes to stand for substance and fact, through its brute materiality. In order to understand purse limits and why and how they matter, this afterword takes inspiration from other experts trained in the tricks of money’s matter: those who conjure with it, and those who count it. Magicians, and bill sorters. Mobile Money Mobile money is a rapidly growing business, propelled in large measure by the interest it has generated from people in the philanthropic and development sectors, who see in mobile money the potential to provide financial access to many ‘unbanked’ poor in the developing world. Money is expensive to store and to send to one’s friends and relatives, especially for those who lack access to financial institutions. Additionally, such financial institutions are out of reach for many people in urban slums, remote rural areas, or places lacking basic electrical and financial infrastructures. The mobile phone, by contrast, is by now globally ubiquitous. Over 75% of the world’s population has access to a mobile phone, whether their own or someone else’s, shared in a family, shared in a village, or borrowed for a small fee from a microentrepreneur who sells access and talk time (GSMA 2010). The modal mobile is a simple device that can be preloaded with airtime minutes. Rather than having a subscription-based mobile service, in other words, most of the world’s mobile users ‘top up’ their phones with airtime which they purchase from a mobile agent as they need it. People around the world have been using airtime minutes as a de facto informal currency ever since the mobile telecommunications business started permitting people to send ‘minutes’ to one another over the mobile network. Sending minutes and cashing them out at their local mobile service provider’s shop allows people Journal of Cultural Economy, Vol. 4, No. 3, August 2011 ISSN 1753-0350 print/1753-0369 online/11/030349-11 – 2011 Taylor & Francis DOI: 10.1080/17530350.2011.586857

Femto Cells: Current Status and Future Directions

is a survey paper on the recently developed and rapidly evolving field of femtocells. Quite often, it is noticed that cell-phone signals are strongly attenuated, when indoors, leading to call dropping or poor call quality. Femtocells are mini base stations that are deployed in users' homes so that the user can directly connect to the cellular network through the femtocell instead of the outdoor macrocell, thereby increasing call quality. In the later stages of the paper, we also discuss the integration of the femtocell into the 3G architecture, as well as the various interference issues that the femtocell faces.

Radio Channel Characterization for Moderate Antenna Heights in Forest Areas

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes the results achieved by an experimental campaign whose goal was to characterize the directional propagation channel at 1.9 GHz in forested areas for moderate antenna heights. These experimental results are useful in the context of pedestrian radio-localization systems relying on cellphone signals. Wideband experimental results, which are recorded with transmit-to-receive distances ranging from 40 to 110 m, indicate that the path loss is well modeled by ITU-R Recommendation 833-4. The temporal fading and multipath dispersion are also analyzed. The delay spread, which ranges from 60 to 120 ns, is strongly anticorrelated with the temporal coherence and increases with transmit-to-receive distance. The azimuth spread remains limited, with average values of about 15 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}$</tex></formula>. </para>

The Challenge of Educating in a Highly-Connected and Multitasking World

The Challenge of Educating in a Highly-Connected and Multitasking World

The Stars Are Out in China

BEIJING— China is building a new set of ears tuned to our nearest star. Last month, the government of Inner Mongolia provided land to the National Astronomical Observatories of the Chinese Academy of Sciences for the Chinese Spectral Radioheliograph (CSRH), one of two major ground-based solar instruments that China's scientific community plans for the coming decade. Construction will begin later this month on the $7.3 million facility, which will listen in on radio bursts that could presage coronal mass ejections and solar flares. When directed at Earth, these ionic tidal waves can trigger geomagnetic storms that disable satellites and knock out power grids. Set to open in 2010, CSRH will consist of 40 radio dishes, each 4.5 meters wide. They will be clustered on the steppe in a zone devoid of earthly radio waves—apart from stray cell phone signals—260 kilometers northwest of Beijing. Meanwhile, there's work on a complementary facility, the Frequency-Agile Solar Radiotelescope (FASR). In June, the National Radio Astronomy Observatory (NRAO) and several university partners asked the U.S. National Science Foundation for $25 million to build FASR at Owens Valley Radio Observatory in California. If they receive the funds, the consortium wants to begin building a prototype array at Owens Valley next year, says NRAO's Tim Bastian.

Knock on wood

Some time ago, actor Laurence Fishburne interrupted a Broadway performance to give a piece of his mind to a member of the audience whose cell phone had gone off during the show. I am sure that, at one point or another, you have been similarly annoyed in a public place by an inconsiderate cell-phone user. How can a restaurant or theater owner provide a quiet zone for its customers? IEEE member Hideo Oda of Iwate University (Japan) and his colleagues have been perfecting another line of defense against irresponsible cell-phone users in public places. Based on a patented design, wood magnetic material (1994), Dr. Oda's magnetic wood can be used to panel a room to shield from cell-phone signals. The Japanese investigators settled on wood because it offers more natural, aesthetic options to interior design.