Benchmarking End-to-end Learning of MIMO Physical-Layer Communication

End-to-end data-driven machine learning (ML) of multiple-input multiple-output (MIMO) systems has been shown to have the potential of exceeding the performance of engineered MIMO transceivers, without any a priori knowledge of communication-theoretic principles. In this work, we aim to understand to what extent and for which scenarios this claim holds true when comparing with fair benchmarks. We study closed-loop MIMO, open-loop MIMO, and multi-user MIMO and show that the gains of ML-based communication in the former two cases can be to a large extent ascribed to implicitly learned geometric shaping and bit and power allocation, not to learning new spatial encoders. For MU-MIMO, we demonstrate the feasibility of a novel method with centralized learning and decentralized executing, outperforming conventional zero-forcing. For each scenario, we provide explicit descriptions as well as open-source implementations of the selected neural-network architectures.Comment: 6 pages, 8 figures, conference pape

Die Marburger Pathologie in den Jahren 1918 bis 1921.Eine Betrachtung der Arbeit am Pathologischen Institut zu Marburg vor dem historischen Hintergrund auf Basis der Auswertung der Sektionsakten.

Die vorliegende Arbeit beschäftigt sich mit der Geschichte des Marburger Pathologischen Instituts der Jahre 1918 bis 1921. Grundlage der Untersuchung war die Auswertung der im entsprechenden Zeitraum am Pathologischen Institut angelegten Sektionsakten und die Recherche der einschlägigen Literatur. Gerade die ersten Jahre des Untersuchungszeitraums waren stark durch den Ersten Weltkrieg, dessen Folgen und erhebliche Ressourcen- und Personalknappheit geprägt. Zum Obduktionsgut dieser Periode zählten neben Zivilpersonen besonders in den ersten Jahren des untersuchten Zeitraums auch Soldaten sowie Kriegsgefangene unterschiedlicher Nationen, die in den Lazaretten Marburgs medizinisch betreut wurden. Marburg blieb von der ersten Influenza-Pandemie, der so genannten „Spanischen Grippe“, nicht verschont. Vor allem im Jahr 1918 wurden viele verstorbene Patienten mit „Spanischer Grippe“ obduziert. Hierbei wurden die typischen morphologischen Befunde durch die Marburger Pathologen dokumentiert, die Suche nach der Ätiologie der Erkrankung beruhte jedoch zu diesem Zeitpunkt auf Spekulation. Der dem Institut während des Untersuchungszeitraums vorstehende Ordinarius, Professor Max Hermann Friedrich Löhlein, gilt als renommierter Mediziner und Wissenschaftler seiner Zeit. Wesentliche Arbeitsgebiete Löhleins waren die Erforschung pathologischer Prozesse der Niere sowie bakteriologische Fragestellungen. Eine durch ihn erstmals beschriebene und nach subakut verlaufenden Endokarditiden auftretende Form fokaler Glomerulonephritiden wurde nach ihm benannt

An all-optical buffer based on temporal cavity solitons operating at 10 Gb/s

We demonstrate the operation of an all-optical buffer based on temporal cavity solitons stored in a nonlinear passive fiber ring resonator. Unwanted acoustic interactions between neighboring solitons are suppressed by modulating the phase of the external laser driving the cavity. A new locking scheme is presented that allows the buffer to operate with an arbitrarily large number of cavity solitons in the loop. Experimentally, we are able to demonstrate the storage of 4536 bits of data, written all-optically into the fiber ring at 10 Gb/s, for 1 minute.Comment: 5 pages, 4 figure

GTP-dependent Ca2+ release from rat liver microsomes Vesicle fusion is not required

AbstractThe GTP-dependent calcium release from rat liver microsomes is known to be promoted in the presence of colloids like polyethyleneglycol (PEG), polyvinylpyrrolidine, or albumin. Dawson et al. [(1987) Biochem. J. 244, 87–92] using the ‘fusogen’ PEG have concluded that both GTP-induced calcium efflux and the enhancement of InsP3-promoted calcium release in the presence of GTP could be attributed to a GTP-dependent vesicle fusion. Here, using the more physiological colloid albumin we report that GTP-induced calcium release from rat liver microsomes may not be linked to vesicle fusion

One photon-per-bit receiver using near-noiseless phase-sensitive amplification

Noise fundamentally limits the capacity and reach in all communication links. In optical space communications, noise primarily originates from the detection process and limits the signal fidelity. . Therefore, the receiver sensitivity plays a key role, dictating the minimum power needed to recover the information transmitted. The widely explored approach of using the pulse-position modulation format trades-off sensitivity against receiver bandwidth and thus data-rate. Here we report on a novel, spectrally efficient, approach based on a coherent receiver with a near-noiseless phase-sensitive pre-amplifier operating at room temperature and demonstrate a sensitivity of one photon-per-bit of incident power at a data rate of 10 Gb/s. The results provide a path to future high-capacity inter-satellite and deep space, and other free-space communication linksComment: 12 pages, 3 figure

Phase-coherent lightwave communications with frequency combs

Fiber-optical networks are a crucial telecommunication infrastructure in society. Wavelength division multiplexing allows for transmitting parallel data streams over the fiber bandwidth, and coherent detection enables the use of sophisticated modulation formats and electronic compensation of signal impairments. In the future, optical frequency combs may replace multiple lasers used for the different wavelength channels. We demonstrate two novel signal processing schemes that take advantage of the broadband phase coherence of optical frequency combs. This approach allows for a more efficient estimation and compensation of optical phase noise in coherent communication systems, which can significantly simplify the signal processing or increase the transmission performance. With further advances in space division multiplexing and chip-scale frequency comb sources, these findings pave the way for compact energy-efficient optical transceivers.Comment: 17 pages, 9 figure

Performance Monitoring for Live Systems with Soft FEC and Multilevel Modulation

Performance monitoring is an essential function for margin measurements in live systems. Historically, system budgets have been described by the Q-factor converted from the bit error rate (BER) under binary modulation and direct detection. The introduction of hard-decision forward error correction (FEC) did not change this. In recent years technologies have changed significantly to comprise coherent detection, multilevel modulation and soft FEC. In such advanced systems, different metrics such as (nomalized) generalized mutual information (GMI/NGMI) and asymmetric information (ASI) are regarded as being more reliable. On the other hand, Q budgets are still useful because pre-FEC BER monitoring is established in industry for live system monitoring. The pre-FEC BER is easily estimated from available information of the number of flipped bits in the FEC decoding, which does not require knowledge of the transmitted bits that are unknown in live systems. Therefore, the use of metrics like GMI/NGMI/ASI for performance monitoring has not been possible in live systems. However, in this work we propose a blind soft-performance estimation method. Based on a histogram of log-likelihood-values without the knowledge of the transmitted bits, we show how the ASI can be estimated. We examined the proposed method experimentally for 16 and 64-ary quadrature amplitude modulation (QAM) and probabilistically shaped 16, 64, and 256-QAM in recirculating loop experiments. We see a relative error of 3.6%, which corresponds to around 0.5 dB signal-to-noise ratio difference for binary modulation, in the regime where the ASI is larger than the assumed FEC threshold. For this proposed method, the digital signal processing circuitry requires only a minimal additional function of storing the L-value histograms before the soft-decision FEC decoder.Comment: 9 pages, 9 figure

Standards – Margins – New Horizons II: Einleitung

Die Einleitung führt in das Themenheft „Standards – Margins – New Horizons II“ ein, in dem die Beiträge der gleichnamigen Konferenz dokumentiert sind, die im Frühjahr 2022 an der Universität Bielefeld stattfand. Diese stellen die Fortsetzung der ersten New Horizons-Konferenz vom Frühjahr 2019 dar, die 2020 als Themenheft der Zeitschrift PFLB (4. Jg., H. 2) dokumentiert wurde. Die Beiträge der „New Horizons II“ diskutieren die Frage, welche sprachlichen, literarischen und kulturellen Kanones für den Fremdsprachenunterricht des 21. Jahrhunderts in den neuen und alten Sprachen maßgeblich sein sollten. Sie widmen sich dabei auch der Problemstellung, welche impliziten und expliziten Kanones derzeitig ausgemacht werden können, welche Akteur*innen diese propagieren und welche Machtstrukturen daraus ersichtlich werden. Die Beiträge überlegen weiterhin, welche Kriterien und Leitlinien für die Canons für 21st-century Teaching genutzt werden können sowie welche konkreten Texte dabei in den Blick geraten. Übergreifend fragen die Beiträge außerdem, was fremdsprachliche Bildung im 21. Jahrhundert bedeutet und welche professionstheoretischen Implikationen sich daraus ergeben. Die neunzehn Beiträge sind in vier Sektionen gegliedert: Critical Literacy, Literaturwissenschaft und Literaturdidaktik, Sprache und Sprachvariation sowie Digitalität

Counterpropagating dipole-mode vector soliton

We experimentally observe a counterpropagating dipole-mode vector soliton in a photorefractive SBN:60Ce crystal. We investigate the transient formation dynamics and show that the formation process differs significantly from the copropagating geometry. The experimental results are compared with fully anisotropic numerical simulations which show good qualitative agreement.Comment: 4 pages, 4 figure