Finite-Blocklength Bounds on the Maximum Coding Rate of Rician Fading Channels with Applications to Pilot-Assisted Transmission

We present nonasymptotic bounds on the maximum coding rate achievable over a Rician block-fading channel for a fixed packet size and a fixed packet error probability. Our bounds, which apply to the scenario where no a priori channel state information is available at the receiver, allow one to quantify the tradeoff between the rate gains resulting from the exploitation of time-frequency diversity and the rate loss resulting from fast channel variations and pilot-symbol overhead

Short Packets over Block-Memoryless Fading Channels: Pilot-Assisted or Noncoherent Transmission?

We present nonasymptotic upper and lower bounds on the maximum coding rate achievable when transmitting short packets over a Rician memoryless block-fading channel for a given requirement on the packet error probability. We focus on the practically relevant scenario in which there is no \emph{a priori} channel state information available at the transmitter and at the receiver. An upper bound built upon the min-max converse is compared to two lower bounds: the first one relies on a noncoherent transmission strategy in which the fading channel is not estimated explicitly at the receiver; the second one employs pilot-assisted transmission (PAT) followed by maximum-likelihood channel estimation and scaled mismatched nearest-neighbor decoding at the receiver. Our bounds are tight enough to unveil the optimum number of diversity branches that a packet should span so that the energy per bit required to achieve a target packet error probability is minimized, for a given constraint on the code rate and the packet size. Furthermore, the bounds reveal that noncoherent transmission is more energy efficient than PAT, even when the number of pilot symbols and their power is optimized. For example, for the case when a coded packet of $168$ symbols is transmitted using a channel code of rate $0.48$ bits/channel use, over a block-fading channel with block size equal to $8$ symbols, PAT requires an additional $1.2$ dB of energy per information bit to achieve a packet error probability of $10^{-3}$ compared to a suitably designed noncoherent transmission scheme. Finally, we devise a PAT scheme based on punctured tail-biting quasi-cyclic codes and ordered statistics decoding, whose performance are close ($1$ dB gap at $10^{-3}$ packet error probability) to the ones predicted by our PAT lower bound. This shows that the PAT lower bound provides useful guidelines on the design of actual PAT schemes.Comment: 30 pages, 5 figures, journa

Low-latency Ultra Reliable 5G Communications: Finite-Blocklength Bounds and Coding Schemes

Future autonomous systems require wireless connectivity able to support extremely stringent requirements on both latency and reliability. In this paper, we leverage recent developments in the field of finite-blocklength information theory to illustrate how to optimally design wireless systems in the presence of such stringent constraints. Focusing on a multi-antenna Rayleigh block-fading channel, we obtain bounds on the maximum number of bits that can be transmitted within given bandwidth, latency, and reliability constraints, using an orthogonal frequency-division multiplexing system similar to LTE. These bounds unveil the fundamental interplay between latency, bandwidth, rate, and reliability. Furthermore, they suggest how to optimally use the available spatial and frequency diversity. Finally, we use our bounds to benchmark the performance of an actual coding scheme involving the transmission of short packets

Недифференцированная дисплазия соединительной ткани и малые аномалии сердца как предиктор развития нарушений ритма у пациентов с ишемической болезнью сердца

ОНТОГЕНЕЗМОРФОГЕНЕЗИШЕМИЧЕСКАЯ БОЛЕЗНЬ СЕРДЦ

Структурно-цитохимические особенности развивающихся почек крысят при антенатальном воздействии инкорпорированных радионуклидов

ГЛИКОПРОТЕИНЫПОЧКИРАДИОАКТИВНЫЕ ИЗОТОПЫРАДИОНУКЛИД

En analys av Holmen Skogs KORUS uppföljning för gallringar

Holmen Skog gör flera uppföljningar på deras gallringar och ville undersöka hur väl entreprenörernas egenuppföljning KORUS överensstämde med den Distriktinventering de själva utför. I analysen gjordes jämförelser för att se ifall det fanns signifikanta skillnader i uppgivna grundytor, stickvägsbredder och stickvägsavstånd. Analyserna gjordes på uppföljningar från Region Örnsköldsvik, från detta datamaterial gjordes enskilda analyser på Distrikt Bredbyn och Distrikt Lycksele. Ytterligare simulerades volymutveckling på de trakter där mätningarna skilde sig mest åt för att se vad felaktiga skattningar kan innebära. Hypotesen var att entreprenörerna överskattade grundytan då de använder en subjektiv metod vilket skulle visa sig vid jämförandet mot Distriktsinventeringen som är en mera objektiv metod. Jämförelsen gjordes parvis på trakter och medeltal beräknades. För att se ifall det fanns signifikanta skillnader mellan uppföljningarna gjordes parade t-test för de undersökta parametrarna. Vid jämförelser visade det sig att mätningarna av stickvägsbredd i de olika uppföljningarna hade en signifikant skillnad, stickvägsbredden i KORUS var lägre. Mätningarna på grundyta och stickvägsavstånd visade sig inte ha någon signifikant skillnad. Felskattning av grundyta i den grad den gjorts på enskilda objekt kan leda till skillnader i virkesförråd vid lägsta slutavverkningsålder på upp till 87 m3sk/ha. Jämförelserna visade att mätningarna överensstämde över förväntan på det samlade datasetet. Entreprenörernas subjektiva metod gav ett mycket tillfredställande resultat överlag men kunde på enskilda trakter skilja mycket från den mer systematiska Distriktinventeringen. Trakter med stora skillnader i mätningar kan vid prognoser av framtida virkesuttag avvika mycket från det verkliga utfallet.Holmen Skog makes follow-ups on their thinning and wanted to investigate how well the contractors own monitoring “KORUS” correlates with their own “Distriktinventeringen”. In the analysis, comparisons were made to see if there were significant differences in reported basal area, strip road widths and strip road spacing. Analyses were made on follow-ups from Region Örnsköldsvik, from this data we made individual analyses on District Bredbyn and District Lycksele. Simulations of volume growth were made on the tracts where the measurements differed most to see what erroneous estimates may entail. The hypothesis was that the contractors overestimated the basal area because they use a subjective method for measuring in comparison to “Distriktsinventeringen” which is a more objective method. The comparison was made on paired tracts and averages were calculated. To see if there were significant differences between the follow-up methods a paired t-test was used to analyse the parameters we wanted to examine. The comparisons revealed that the measurements of the strip road width in the different follow-ups had a significant difference, in KORUS the width was lower. Measurements of basal area and service road spacing had no significant difference. Volume differences of up to 87 m3/ha at earliest recommended clear cutting age were simulated. The comparisons showed that the measurements were consistent over the overall dataset. Contractors subjective method gave a very satisfactory result overall but could on individual tracts differ much from the more systematic “Distriktsinventeringen”. The tracts with large differences in measurements can at forecasts of future timber extraction deviate much from the actual outcome

Short-packet Transmission via Variable-Length Codes in the Presence of Noisy Stop Feedback

We present an upper bound on the error probability achievable using variable-length stop feedback codes, for a fixed size of the information payload and a given constraint on the maximum latency and the average service time. Differently from the bound proposed in Polyanskiy et al. (2011), which pertains to the scenario in which the stop signal is sent over a noiseless feedback channel, our bound applies to the practically relevant setup in which the feedback link is noisy. By numerically evaluating our bound, we illustrate that, for fixed latency and reliability constraints, noise in the feedback link can cause a significant increase in the minimum average service time, to the extent that fixed-length codes without feedback may be preferable in some scenarios.Comment: Submitted to a Transactions on Wireless Communication

Erilaistamisen sietämätön keveys : Ruotsi, Suomi ja pitkä yhteinen historia

Analyysi YLEn "Suomi on ruotsalainen" -televisiosarjasta

Magnetic order and energy-scale hierarchy in artificial spin ice

In order to explain and predict the properties of many physical systems, it is essential to understand the interplay of different energy-scales. Here we present investigations of the magnetic order in thermalised artificial spin ice structures, with different activation energies of the interacting Ising-like elements. We image the thermally equilibrated magnetic states of the nano-structures using synchrotron-based magnetic microscopy. By comparing results obtained from structures with one or two different activation energies, we demonstrate a clear impact on the resulting magnetic order. The differences are obtained by the analysis of the magnetic spin structure factors, in which the role of the activation energies is manifested by distinct short-range order. This demonstrates that artificial spin systems can serve as model systems, allowing the definition of energy-scales by geometrical design and providing the backdrop for understanding their interplay.Comment: 8 pages, 5 figures (+ supplementary 6 pages, 4 figures