On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining

Capitalizing on the recently proposed Fisher-Snedecor F composite fading model, in this letter, we investigate the sum of independent but not identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel closed-form expression is derived for the moment generating function of the instantaneous signal-to-noise ratio. Based on this, the corresponding probability density function and cumulative distribution function of the sum of i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently employed in the analysis of multiple branch maximal-ratio combining (MRC). Specifically, we investigate the impact of multipath and shadowed fading on the outage probability and outage capacity of MRC based receivers. In addition, we derive exact closed-form expressions for the average bit error rate of coherent binary modulation schemes followed by an asymptotic analysis which provides further insights into the effect of the system parameters on the overall performance. Importantly, it is shown that the effect of multipath fading on the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure

Respiration and Heart Rate at the Surface between Dives in Northern Elephant Seals

All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fb) and heart rate (fh) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fb and fh acoustically in six translocated juveniles, 1.8-2. 4 years old, and three migrating adult males from the rookery at Ano Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fh at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2+/−0.4 min, adult males breathed a mean of 32.7+/−5.4 times at a rate of 15. 3+/−1.8 breaths min(−)(1) (means +/− s.d., N=57). Mean fh at the surface was 84+/−3 beats min(−)(1). The fb of juveniles was 26 % faster than that of adult males, averaging 19.2+/−2.2 breaths min(−)(1) for a mean total of 41.2+/−5.0 breaths during surface intervals lasting 2.6+/−0.31 min. Mean fh at the surface was 106+/−3 beats min(−)(1). fb and fh did not change significantly over the course of surface intervals. Surface fb and fh were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores

Approximate Distributions of the Residual Self-Interference Power in Multi-tap Full-Duplex Systems

In this letter, we investigate closed-form distributions to approximate the power of the residual Self-Interference (SI) due to: 1) uncanceled signals transmitted over multiple delay-taps, and 2) the presence of radio frequency and transceiver impairments, of an In-Band Full-duplex (IBFDX) wireless system. Starting with the distribution of the residual SI power for a single tap, we extend the analysis for multiple taps comparing two different solutions. The first one is based on the Welch-Satterthwaite (W-S) approximation, while the second is a moment-based approximation to an α-μ distribution. When compared to empirical results obtained by simulation, our work shows that the distribution of the residual SI power can be accurately represented by the W-S approximation when the uncertainty level of the fading in the different taps is low. However, for higher levels of uncertainty we show that the α-μ moment-based approximation is more accurate. A comparison between simulated and numerical results show the effectiveness of the proposed model.authorsversionpublishe

A Better Approach for Mishandled Bags Industry Measure

Since 1987, the US Department of Transportation (DOT) has ordered US airlines to report baggage handling statistics. The Code of Federal Regulations (CFR), requests each U.S. carrier to report monthly the total number of passengers enplaned, and the total number of mishandled baggage reports (MBR), including lost, pilfered, damaged and delayed baggage. The U.S. DOT also created a mishandled-baggage rate, which represents the total number of MBRs divided by 1,000 passengers enplaned. This KPI is monthly published at the Air Travel Consumer Report. And it is used worldwide to make comparisons between regions, airports, and airlines, characterizing efficiency and consistency in service and setting a benchmark for the industry. The problem with this indicator created in 1987 is that it only considers passengers, not checked baggage. The customer\u27s behavior has changed a lot after airlines started charging for the checked baggage, influencing KPI results. Therefore, in January 2019 US DOT proposed a new mishandled bags KPI for the airline industry, instead of dividing the original KPI per 1,000 passengers, the new KPI proposes dividing the total number of mishandled baggage report per 1,000 checked baggage. This KPI considers checked bags, correcting this flaw, and creates a more accurate and reliable indicator, avoiding incorrect investment decisions and loss of money. Desde 1987, o Departamento de Transportes dos Estados EUA (DOT) ordena que as companhias aéreas dos EUA reportem as estatísticas de manuseio de bagagem. O Código de Regulamentos Federais (CFR) solicita a cada transportadora dos EUA que reporte mensalmente o número total de passageiros embarcados e o número total de relatórios de bagagem extraviada (MBR), incluindo bagagem perdida, furtada, danificada e atrasada. O DOT dos EUA também criou um índice de bagagem extraviadas, que representa o número total de MBRs dividido por 1.000 passageiros embarcados. Este KPI é publicado mensalmente no Air Travel Consumer Report. E é usado em todo o mundo para fazer comparações entre regiões, aeroportos e companhias aéreas, caracterizando eficiência e consistência no serviço e estabelecendo uma referência para o setor. O problema com esse indicador criado em 1987 é que ele considera apenas passageiros, não bagagem despachada. O comportamento do cliente mudou muito depois que as companhias aéreas começaram a cobrar pela bagagem despachada, influenciando os resultados do KPI. Portanto, este estudo propõe um novo KPI de malas mal manejadas para o setor aéreo. Esse KPI considera as malas despachadas, corrigindo essa falha e cria um indicador mais preciso e confiável, evitando decisões incorretas de investimento e perda de dinheiro

Casimir energy in a small volume multiply connected static hyperbolic pre-inflationary Universe

A few years ago, Cornish, Spergel and Starkman (CSS), suggested that a multiply connected ``small'' Universe could allow for classical chaotic mixing as a pre-inflationary homogenization process. The smaller the volume, the more important the process. Also, a smaller Universe has a greater probability of being spontaneously created. Previously DeWitt, Hart and Isham (DHI) calculated the Casimir energy for static multiply connected flat space-times. Due to the interest in small volume hyperbolic Universes (e.g. CSS), we generalize the DHI calculation by making a a numerical investigation of the Casimir energy for a conformally coupled, massive scalar field in a static Universe, whose spatial sections are the Weeks manifold, the smallest Universe of negative curvature known. In spite of being a numerical calculation, our result is in fact exact. It is shown that there is spontaneous vacuum excitation of low multipolar components.Comment: accepted for publication in phys. rev.

Cognitive full-duplex relay networks under the peak interference power constraint of multiple primary users

Abstract This paper investigates the outage performance of cognitive spectrum-sharing multi-relay networks in which the relays operate in a full-duplex (FD) mode and employ the decode-and-forward (DF) protocol. Two relay selection schemes, i.e., partial relay selection (PRS) and optimal relay selection (ORS), are considered to enhance the system performance. New exact expressions for the outage probability (OP) in both schemes are derived based on which an asymptotic analysis is carried out. The results show that the ORS strategy outperforms PRS in terms of OP, and increasing the number of FD relays can significantly improve the system performance. Moreover, novel analytical results provide additional insights for system design. In particular, from the viewpoint of FD concept, the primary network parameters (i.e., peak interference at the primary receivers, number of primary receivers, and their locations) should be carefully considered since they significantly affect the secondary network performance