Picture of Daniel Plabst

M.Sc. Daniel Plabst

Technical University of Munich

Associate Professorship of Line Transmission Technology (Prof. Hanik)

Postal address

Postal:
Theresienstr. 90
80333 München

Biography

I received my M.Sc. degree from the Technical University of Munich (TUM) in 2018.

In my Master's thesis I worked on signal processing for energy-efficient wireless communication systems at the Associate Professorship of Signal Processing (MSV), while staying with the Wireless Networking and Communications Group at the University of Texas at Austin (UT), USA.

Since 2019 I am a research assistant at the Institute for Communications Engineering in the group Line Transmission Technology of Prof. Dr.-Ing. Norbert Hanik.

Research Interests

Direct-Detection (DD) is a cost-effective approach for short-reach fiber-optic communication. A DD receiver uses a single photodiode to measure the intensity of the impinging signal. This suggests that DD is not compatible with phase modulation. However, using oversampling, the phase can be recovered by exploiting inter-symbol interference (ISI).

We investigate DD for short-reach communication in the context of information theory and estimation strategies.

Theses

Available Theses

Neural Networks (NNs) for Direct Detection

Description

In [1] we consider a short-reach fiber-optic link with a single photodiode at the receiver, which is a so-called direct detector (DD). The DD outputs a signal, propotional to the squared magnitude of its input. At first glance, this makes phase modulation challgenging. In [1] we showed that inter-symbol intereference (ISI) can be used to retrieve the phase. A suboptimal symbol-wise MAP detector was then proposed for phase retrieval. However, the detector exhibits a large complexity, which grows exponentially in the amount of ISI.

The task of the student is to efficiently approximate the MAP detector using a NN.  An appropriate NN type/structure needs to be selected. Finally, lower bounds on the achievable rates are computed to evaluate the performance of the NN and compare it to the MAP detector [1].

[1] D. Plabst et al., "Achievable Rates for Short-Reach Fiber-Optic Channels With Direct Detection," in Journal of Lightwave Technology, vol. 40, no. 12, pp. 3602-3613, 15 June15, 2022, doi: 10.1109/JLT.2022.3149574.

 

 

Prerequisites

Machine Learning

Statistical Signal Processing

Supervisor:

Capacity upper Bounds for ISI Channels with Direct Detection

Description

We are interested in computing upper bounds (on capacity) for frequency-selective channels with a memoryless nonlineary at the transmitter/receiver.

One application for these bounds are short-reach fiber-optic communication systems with a single photodiode at the receiver. The photodiode is a memoryless nonlinearity, as it produces an output that is proportional to the squared magnitude of the input signal.

A simple upper bound for the above model is given in [Sec. III D, 2].

D. Plabst et al., "Achievable Rates for Short-Reach Fiber-Optic Channels With Direct Detection," in Journal of Lightwave Technology, vol. 40, no. 12, pp. 3602-3613, 15 June15, 2022, doi: 10.1109/JLT.2022.3149574.

 

 

Prerequisites

Information Theory

Linear System Theory

Supervisor:

Capacity Lower Bounds for ISI Channels

Description

Capacity and capacity-achieving distributions are available for some memoryless channels. For the average-power constrained memoryless channel with additive white Gaussian noise, Shannon provided a closed form description of capacity. Closed form solutions for capacity also exist for some simple discrete memoryless channels (DMCs). In addition, numerical algorithms for calculating the capacity (and capacity-achieving discrete distributions) of general DMCs are available through the works of Arimoto and Blahut.

However, often wireless or fiber-optic channels of practical interest contain intersymbol interference (ISI), and the memory due to ISI can no longer be neglected. When considering discrete channel inputs, one may be interested in determining the capacity and capacity-achieving distribution for these ISI channels. In fact, discrete stationary Markov processes asymptotically achieve the capacity of finite-state ISI channels as the order of the Markov process goes to infinity.

An algorithm [1] for optimizing discrete Markov processes of a certain order M is presented to maximize the information rate between channel input and output. As the order of the Markov process increases, tighter lower bounds on capacity are obtained.

[1] A. Kavcic, "On the capacity of Markov sources over noisy channels," GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 2001, pp. 2997-3001 vol.5, doi: 10.1109/GLOCOM.2001.965977.

Further reading (if required):

[2] P. O. Vontobel, A. Kavcic, D. M. Arnold and H. -A. Loeliger, "A Generalization of the Blahut–Arimoto Algorithm to Finite-State Channels," in IEEE Transactions on Information Theory, vol. 54, no. 5, pp. 1887-1918, May 2008, doi: 10.1109/TIT.2008.920243.

[3] T. Lang, A. Mezghani and J. A. Nossek, "Channel-matched trellis codes for finite-state intersymbol-interference channels," 2010 IEEE 11th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2010, pp. 1-5, doi: 10.1109/SPAWC.2010.5670890.

Prerequisites

Information Theory

Supervisor:

Theses in Progress

Publications

2022

  • Plabst, D.; Prinz, T.; Wiegart, T.; Rahman, T.; Stojanovic, N.; Calabro, S.; Hanik, N.; Kramer, G.: Achievable Rates for Short-Reach Fiber-Optic Channels with Direct Detection. IEEE/OSA J. Lightw. Technol., 2022 more… Full text ( DOI )
  • Prinz, T.; Wiegart, T.; Plabst, D.; Rahman, T.; Hossain, S.; Stojanović, N.; Calabrò, S.; Hanik, N.; Kramer, G.: Comparison of PAM-6 Modulations for Short-Reach Fiber-Optic Links with Intensity Modulation and Direct Detection. European Conference on Optical Communication (ECOC) 2022, 2022 more… Full text ( DOI )
  • Wiegart, T.; Plabst, D.; Prinz, T.; Rahman, T.; Schädler, M.; Stojanović, N.; Calabrò, S.; Hanik, N.; Kramer, G.: Experiments on Bipolar Transmission with Direct Detection. European Conference on Optical Communication (ECOC) 2022, 2022 more… Full text ( DOI )

2021

  • Mezghani A., Plabst D., Swindlehurst L. A. , Fijalkow I., Nossek J. A.: Sparse Linear Precoders for Mitigating Nonlinearities in Massive MIMO. IEEE Statistical Signal Processing Workshop 2021, 2021 more…
  • Prinz, T.; Wiegart, T.; Plabst, D.; Calabrò, S.; Böcherer, G.; Stojanovic, N.; Rahman, T.;: PAM-6 Coded Modulation for IM/DD Channels with a Peak-Power Constraint. International Symposium on Topics in Coding (ISTC) 2021, 2021 more…
  • Wiegart, T.; Prinz, T.; Plabst, D.: Recovering the Phase in DD Receivers with Oversampling: A Toy Example. Huawei Joint Lab Workshop, 2021 more…

2020

  • Benedikt Leible, Daniel Plabst, Norbert Hanik: Back-to-Back Performance of the Full Spectrum Nonlinear Fourier Transform and Its Inverse. Entropy 22 (10), 2020, 1131 more… Full text ( DOI ) Full text (mediaTUM)
  • Benedikt Leible, Daniel Plabst, Norbert Hanik: Stability of the Full Spectrum Nonlinear FourierTransform. International Conference on Transparent Optical Networks (ICTON) 2020, 2020 more… Full text (mediaTUM)
  • Plabst, D.; Hanik, N.: Phase-Retrieval for Short-Reach IM/DD Links. Workshop der Informationstechnischen Gesellschaft (ITG) in Karlsruhe, 2020 more…
  • Plabst, Daniel; García-Gómez, Francisco Javier; Wiegart, Thomas; Hanik, Norbert: Wiener Filter for Short-Reach Fiber-Optic Links. IEEE Communications Letters 24 (11), 2020, 2546 - 2550 more… Full text ( DOI )

2019

  • Plabst, D.; Jedda, H.; Mezghani A.: Linear Transmit Signal Processing in 1-Bit Quantized Massive MIMO Systems. 2019 Munich Doctoral Seminar on Communications, 2019 more… Full text (mediaTUM)

2018

  • Munir, J.; Plabst, D.; Nossek, J.A.: Efficient Equalization Method for Cyclic Prefix-Free Coarsely Quantized Massive MIMO Systems. 2018 IEEE International Conference on Communications (ICC), 2018 more… Full text ( DOI )
  • Plabst, D.; Munir J.; Mezghani A.; Nossek, J.A.: Efficient Non-linear Equalization for 1-bit Quantized Cyclic Prefix-Free Massive MIMO Systems. 2018 15th International Symposium on Wireless Communication Systems (ISWCS), 2018 more… Full text ( DOI )