Characteristics of the complex received signal in dynamic body area networks

This paper investigates the characteristics of the complex received signal in body area networks for two environments at the opposite ends of the multipath spectrum at 2.45 GHz. Important attributes of the complex channel such as the Gaussianity of the quadrature components and power imbalance, which form the basis of many popular fading models, are investigated. It is found that in anechoic environments the assumption of Gaussian distributed quadrature components will not always yield a satisfactory fit. Using a complex received signal model which considers a non-isotropic scattered signal contribution along with the presence of an optional dominant signal component, we use an autocorrelation function originally derived for mobile-to-mobile communications to model the temporal behavior of a range of dynamic body area network channels with considerable success. In reverberant environments, it was observed that the real part of the complex autocorrelation function for body area network channels decayed slightly quicker than that expected in traditional land mobile channels. © 2013 IEEE.

Creating secure wireless regions using configurable beamforming

We present a novel approach to network security against passive eavesdroppers by employing a configurable beam-forming technique to create tightly defined regions of coverage for targeted users. In contrast to conventional encryption methods, our security scheme is developed at the physical layer by configuring antenna array beam patterns to transmit the data to specific regions. It is shown that this technique can effectively reduce vulnerability of the physical regions to eavesdropping by adapting the antenna configuration according to the intended user's channel state information. In this paper we present the application of our concept to 802.11n networks where an antenna array is employed at the access point, and consider the issue of minimizing the coverage area of the region surrounding the targeted user. A metric termed the exposure region is formally defined and used to evaluate the level of security offered by this technique. A range of antenna array configurations are examined through analysis and simulation, and these are subsequently used to obtain the optimum array configuration for a user traversing a coverage area.

Localization Algorithm Performance in Ultra Low Power Active RFID Based Patient Tracking

Indoor personnel localization research has generated a range of potential techniques and algorithms. However, these typically do not account for the influence of the user's body upon the radio channel. In this paper an active RFID based patient tracking system is demonstrated and three localization algorithms are used to estimate the location of a user within a modern office building. It is shown that disregarding body effects reduces the accuracy of the algorithms' location estimates and that body shadowing effects create a systematic position error that estimates the user's location as closer to the RFID reader that the active tag has line of sight to.

Low complexity greedy detection method with generalized multicarrier index keying OFDM

Multicarrier Index Keying (MCIK) is a recently developed technique that modulates subcarriers but also indices of the subcarriers. In this paper a novel low-complexity detection scheme of subcarrier indices is proposed for an MCIK system and addresses a substantial reduction in complexity over the optimalmaximum likelihood (ML) detection. For the performance evaluation, a closed-form expression for the pairwise error probability (PEP) of an active subcarrier index, and a tight approximation of the average PEP of multiple subcarrier indices are derived in closed-form. The theoretical outcomes are validated usingsimulations, at a difference of less than 0.1dB. Compared to the optimal ML, the proposed detection achieves a substantial reduction in complexity with small loss in error performance (<= 0.6dB).

The κ− μ / Inverse Gamma Fading Model

Statistical distributions have been extensively used in modeling fading effects in conventional and modern wireless communications. In the present work, we propose a novel κ − µ composite shadowed fading model, which is based on the valid assumption that the mean signal power follows the inverse gamma distribution instead of the lognormal or commonly used gamma distributions. This distribution has a simple relationship with the gamma distribution, but most importantly, its semi heavy-tailed characteristics constitute it suitable for applications relating to modeling of shadowed fading. Furthermore, the derived probability density function of the κ − µ / inverse gamma composite distribution admits a rather simple algebraic representation that renders it convenient to handle both analytically and numerically. The validity and utility of this fading model are demonstrated by means of modeling the fading effects encountered in body centric communications channels, which have been known to be susceptible to the shadowing effect. To this end, extensive comparisons are provided between theoretical and respective real-time measurement results. It is shown that these comparisons exhibit accurate fitting of the new model for various measurement set ups that correspond to realistic communication scenarios.

The η − µ / Inverse Gamma Composite Fading Model

In this paper we propose a new composite fadingmodel which assumes that the mean signal power of an η−µ signalenvelope follows an inverse gamma distribution. The inversegamma distribution has a simple relationship with the gammadistribution and can be used to model shadowed fading due to itssemi heavy-tailed characteristics. To demonstrate the utility of thenew η−µ / inverse gamma composite fading model, we investigatethe characteristics of the shadowed fading behavior observed inbody centric communications channels which are known to besusceptible to shadowing effects, particularly generated by thehuman body. It is shown that the η−µ / inverse gamma compositefading model provided an excellent fit to the measurement data.Moreover, using Kullback-Leibler divergence, the η −µ / inversegamma composite fading model was found to provide a better fitto the measured data than the κ − µ / inverse gamma compositefading model, for the communication scenarios considered here.

A Low Complexity Detector with MRC Diversity Reception for MCIK-OFDM

Multi-carrier index keying (MCIK) is a recently developed transmission technique that exploits the sub-carrier indices as an additional degree of freedom for data transmission. This paper investigates the performance of a low complexity detection scheme with diversity reception for MCIK with orthogonal frequency division multiplexing (OFDM). For the performance evaluation, an exact and an approximate closed form expression for the pairwise error probability (PEP) of a greedy detector (GD) with maximal ratio combining (MRC) is derived. The presented results show that the performance of the GD is significantly improved when MRC diversity is employed. The proposed hybrid scheme is found to outperform maximum likelihood (ML) detection with a substantial reduction on the associated computational complexity.

New Opportunities for Development Journalism: Enlarging the Public Sphere with ICTs

The present study examines new opportunities offered by the introduction of information and communication technologies (ICTs) to enhance the development journalism practice, in order to enlarge the public sphere and empower ordinary people to participate more actively in public debate on issues affecting their development. The analysis of the achievements and challenges faced by 32 radio stations under the UNESCO project “Empowering Local Radios with ICTs” offers an overview of the introduction of ICTs in different contexts, within and among seven countries in Sub- Saharan Africa. Even though the lack of ICTs access and knowledge is still a concern in the developing world, especially in rural areas, these new tools can be adapted to each context and foster a more pluralistic and participative media in order to address people’s needs and promote social change.

John W. Fisher Fonds, 1937-1961, 1964-1989, 1993, n.d.

Norah and Fred Fisher welcomed John Fisher into the world on November 29, 1912, not knowing what an influential role he would play in shaping Canada's history. John Fisher grew up as the middle child of five brothers and sisters in Frosty Hollow, New Brunswick, close to today’s town of Sackville. Sackville’s main industry was the Enterprise Foundry which the Fisher family owned and operated; however, Fisher had no plans of going into the family business. He was more inspired by his maternal grandfather, Dr. Cecil Wiggins, who lived with the family after retiring from the Anglican ministry. Wiggins encouraged all his grandchildren to be well read and to take part in discussions on current events. There were often visitors in the Fisher household taking part in discussions about politics, religion, and daily life. Fisher forced himself to take part in these conversations to help overcome his shyness in social settings. These conversations did help with his shyness and also in forming many opinions and observations about Canada. It put Fisher on the road to becoming Mr. Canada and delivering the many eloquent speeches for which he was known. Fisher did not venture far from home to complete his first degree. In 1934 he graduated from Mount Allison University in Sackville, NB with an Arts degree. The same year Fisher enrolled in Dalhousie’s law school. During his time at Dalhousie, Fisher discovered radio through Hugh Mills. Mills or “Uncle Mel” was on CHNS, Halifax’s only radio station at the time. Fisher began by making appearences on the radio drama show. By 1941 he had begun writing and broadcasting his own works and joined the staff as an announcer and continuity writer. In 1936 the Canadian Broadcasting Corporation was formed, the first National radio station. Fisher joined the CBC shortly after it’s beginning and remained with them, as well as the Halifax Herald newspaper, even after his law school graduation in 1937. By 1943 Fisher’s talks became a part of the CBC’s programming for a group of maritime radio stations. Fisher once described his talks as follows “my talks weren’t meant to be objective. . . they were meant to be favourable. They were ‘pride builders’” He began his famed John Fisher Reports at CBC Toronto when he transfered there shortly after the war. This program brought emmence pride to the fellow Canadians he spoke about leading to approximately 3500 requests per year to speak at banquets and meeting throughout Canada and the United States. Fisher was a well travelled indivdual who would draw on personal experiences to connect with his audience. His stories were told in simple, straight forward language for anyone to enjoy. He became a smooth, dynamic and passionate speaker who sold Canada to Canadians. He became a renowned journalist, folk historian, writer and broadcaster. Fisher was able to reach a vast array of people through his radio work and build Canadian pride, but he did not stop there. Other ways Fisher has contributed to Canada and the Canadian people include: Honoured by five Canadian Universities. 1956, became the Director of the Canadian Tourist Association. 1961, was appointed Special Assistant to the Prime Minister of Canada. 1963, Commissioner of the Centennial Commission (the Federal Agency Responsible for Canada’s 100th birthday) 1968, received the Service Medal , a coveted Order of Canada. President of John Fisher Enterprises Ltd., private consultant work, specializing in Centennial planning, broadcasts, lectures and promotion. John Fisher continued recording radio broadcasts even after his diagnosis with cancer. He would record 3 or 4 at a time so he was free to travel across Canada, the U.S., Europe and Mexico in search of treatments. Fisher passed away from the disease on February 15, 1981 and he is buried at Mount Pleasant Cemetery in Toronto.

A multiple-building diffraction attenuation function expressed in terms of UTD coefficients for microcellular communications

This work presents an explicit formulation for multiple- edge diffraction for mobile radiowave propagation in terms of uniform theory of diffraction (UTD) coefficients when a spherical incident wave is considered. This solution can be used in an UTD context and sharply reduces the computing time over existing formulation. Results can be applied in the planning of microcellular systems

Twitter en Colombia: ¿Cómo lo están usando las cadenas radiales para informar?

En Colombia los medios de comunicación, más específicamente las cadenas radiales nacionales más importantes, no se han quedado atrás y han optado por unirse desde hace unos años a twitter, incursionando sobre la marcha. Las cuentas de twitter de Bluradio, Caracol Radio y RCN Radio analizadas junto a las entrevistas con los encargados de las mismas y las emisiones de los programas de noticias escogidos, muestran que las redes sociales siguen siendo un desafío en la actualidad. Uno de esos desafíos es encontrar el verdadero objetivo de los medios en twitter y que este no sólo consista en la escucha activa en busca de las noticias de último momento. Para alcanzar una legitimidad comunicativa en la web 2.0 es necesario adaptarse a la cultura de la participación de las redes, de lo contrario se está condenado a obtener tan solo un nuevo canal de difusión de noticias.

Cronologia dels programes femenins a la ràdio catalana d’abans de la Guerra Civil

El propòsit d’aquest article és endreçar la cronologia dels programes femenins que les estacions de ràdio pioneres emetien a Catalunya abans de la Guerra Civil i conèixer-ne els trets diferenciadors que tenien. Tal com ja he posat de manifest en les conclusions de la meva tesi doctoral, i en alguns dels articles que se n’han derivat, els programes femenins que les emissores catalanes varen dur a terme abans de 1939 van ser els primers espais de la radiodifusió espanyola que varen tenir el que ara coneixem com a format. Aquesta manera d’entendre un programa de ràdio, que ja va tenir una locutora a finals dels anys vint, ha permès que ara investiguem, per ordenar-los cronològicament, aquests espais tan vells i tan preuats de la ràdio pionera, i que a més a més puguem revelar quines característiques comunes tenien tots aquests espais femenins, a partir de saber els detalls de tots els que varen coincidir, en el temps, a les ones de Barcelona

Performance of GPRS coding scheme detection under severe multipath and co-channel interference as a function of soft-bit width

The General Packet Radio Service (GPRS) has been developed for the mobile radio environment to allow the migration from the traditional circuit switched connection to a more efficient packet based communication link particularly for data transfer. GPRS requires the addition of not only the GPRS software protocol stack, but also more baseband functionality for the mobile as new coding schemes have be en defined, uplink status flag detection, multislot operation and dynamic coding scheme detect. This paper concentrates on evaluating the performance of the GPRS coding scheme detection methods in the presence of a multipath fading channel with a single co-channel interferer as a function of various soft-bit data widths. It has been found that compressing the soft-bit data widths from the output of the equalizer to save memory can influence the likelihood decision of the coding scheme detect function and hence contribute to the overall performance loss of the system. Coding scheme detection errors can therefore force the channel decoder to either select the incorrect decoding scheme or have no clear decision which coding scheme to use resulting in the decoded radio block failing the block check sequence and contribute to the block error rate. For correct performance simulation, the performance of the full coding scheme detection must be taken into account.

Performance of asynchronous channel assignment scheme in non-uniform and dynamic topology WLANs

Dense deployments of wireless local area networks (WLANs) are fast becoming a permanent feature of all developed cities around the world. While this increases capacity and coverage, the problem of increased interference, which is exacerbated by the limited number of channels available, can severely degrade the performance of WLANs if an effective channel assignment scheme is not employed. In an earlier work, an asynchronous, distributed and dynamic channel assignment scheme has been proposed that (1) is simple to implement, (2) does not require any knowledge of the throughput function, and (3) allows asynchronous channel switching by each access point (AP). In this paper, we present extensive performance evaluation of this scheme when it is deployed in the more practical non-uniform and dynamic topology scenarios. Specifically, we investigate its effectiveness (1) when APs are deployed in a nonuniform fashion resulting in some APs suffering from higher levels of interference than others and (2) when APs are effectively switched `on/off' due to the availability/lack of traffic at different times, which creates a dynamically changing network topology. Simulation results based on actual WLAN topologies show that robust performance gains over other channel assignment schemes can still be achieved even in these realistic scenarios.