# Laufende Arbeiten

### Bachelorarbeiten

Characterization of Inter Symbol Interference (ISI) for Non Square Modulation

## Characterization of Inter Symbol Interference (ISI) for Non Square Modulation

**Stichworte: **

ISI, Equalization, Modulation

#### Beschreibung

We aim to reproduce and develop approximate closed form expressions for the ISI after the use of an adaptive equalizer. The modulation constellations might be regular, as well as, non square.

#### Kontakt

delcho.donev@tum.de

#### Betreuer:

Reduced Complexity Digital Back Propagation Algorithms

## Reduced Complexity Digital Back Propagation Algorithms

#### Beschreibung

yle="margin-bottom: 0cm; line-height: 100%;">In the high transmission power regime, the nonlinear effects during propagation are limiting the achievable data rates of WDM systems [1]. One well studied technique, to partially mitigate these effects, is „Digital Back-Propagation“ (DBP) [2]. DBP models the inverse of the optical channel, by the split step Fourier method (SSFM) [3]. Compared to linear compensation schemes, such as chromatic dispersion compensation (CDC), DBP enables higher data-rates, but also increases the receivers complexity.

yle="margin-bottom: 0cm; line-height: 100%;">The students task is to understand the concept of SSFM and DBP and implement several versions of the DBP scheme. These algorithms then have to be evaluated in a WDM system simulation, with two different fiber channel models.

yle="margin-bottom: 0cm; line-height: 100%;">[1] Essiambre - "Capacity Limits of Optical Fiber Networks"

yle="margin-bottom: 0cm; line-height: 100%;">[2] Napoli - "Reduced Complexity Digital Back-Propagation Methods for Optical Communication Systems“

yle="margin-bottom: 0cm; line-height: 100%;">[3] Sinkin - "Optimization of the Split-Step Fourier Method in Modeling Optical-Fiber Communications Systems"

#### Voraussetzungen

No specific requirements (some basics in Matlab might be beneficial but are not strictly needed)

#### Betreuer:

#### Student

Joint Random Errors happen on Partial Defect Cells

## Joint Random Errors happen on Partial Defect Cells

**Stichworte: **

Linear Codes, Algebraic Codes, Error Correction , Masking, defects, non-volatile memories, phase-change memories,PCMs, sagemath

**Kurzbeschreibung: **

So far, all investigated error correction for memory with partial defects works have been done for "disjoint" error such that we suppose the error cannot happen in a position where the memory already partially defects. In this thesis, we want to consider if a joint error happens what are the code constructions for a different number of partially stuck (defect) memory cells up to the code length.

#### Beschreibung

The demand of reliable memory solutions and in particular for non-volatile memories such as phase-change memories (PCMs) for different applications is steadily increasing. The key characteristic of PCM cells is that they can switch between two main states: an amorphous state and a crystalline state. PCM cells may become defect (also called stuck) if they fail in switching their states. This occasionally happens due to the cooling and healing processes of the cells, and therefore cells can only hold a single phase. There are two scenarios of such a defect. Classical stuck cells, i.e. the cell level cannot switch up or down its current level. The other more flexible scenario is partially stuck cells, here, the cell can increase its level but cannot go down its current one.

So far, error-correcting code constructions for defect memory with additional errors have been done. Recent works focus only on the additional error that happens in a position in which the cell assumed is reliable (non-stuck).

In this thesis, we want to investigate the case where error and partially defect cells happen in the same position. Further, a mix-mode of joint and disjoint error could also be considered in this thesis.

#### Voraussetzungen

- Good knowledge of Linear Algebra

- Good knowledge of Channel Coding/Coding Theory

- Basic knowledge in Information Theory

- Programming (Python -- > preferably Sagemath)

#### Kontakt

M.Eng. Haider Al Kim

Doctoral Researcher

Technical University of Munich

Department of Electrical and Computer Engineering /

Coding for Communications and Data Storage (COD) Group

Building N4, Room 3417

Theresienstr. 90, 80333 München

Email: haider.alkim@tum.de

Phone: +49 8928929055

https://www.lnt.ei.tum.de/en/people/doctoral-researchers/alkim/

#### Betreuer:

### Masterarbeiten

Performance and security in identification codes

## Performance and security in identification codes

#### Beschreibung

During the course of this project the student will study the implementation of identification codes aiming at improving their performance in comparison to existing codes and transmission and will study the implementation of security functions that can implement infomation-theoretic semantic security in identification codes.

#### Betreuer:

Identification Over the Arbitrarily Varying Broadcast Channel

## Identification Over the Arbitrarily Varying Broadcast Channel

**Stichworte: **

Identification capacity, broadcast communication, channel with jamming

**Kurzbeschreibung: **

Identification over the arbitrarily broadcast channel with semi-average errors is studied.

#### Beschreibung

The student will characterize the optimal identification rates for a two-receiver broadcast channel with a jammer, in the arbitrarily varying setting. The thesis will include a comparison to the known results from transmission, evaluation of generalized minimax properties for regions, and will study the role of common randomness.

#### Betreuer:

Real-Time Processing and Security Protocols for Continuous-Variable Quantum Key Distribution

## Real-Time Processing and Security Protocols for Continuous-Variable Quantum Key Distribution

**Stichworte: **

Quantum Key Distribution

#### Beschreibung

Continuous-Variable Quantum Key Distribution (CV-QKD) is a method to distribute a secret key between two parties using standard coherent communication equipment. In this thesis, the digital signal processing and security algorithms for CV-QKD will be optimized for real-time processing. The goal is to design and evaluate an online FPGA implementation of the CV-QKD DSP and post-processing.

#### Kontakt

TFehenberger@adva.com

#### Betreuer:

Coding for Distributed Coordinate Gradient Descent

## Coding for Distributed Coordinate Gradient Descent

#### Beschreibung

yle="margin: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 12px; line-height: normal; font-family: 'Helvetica Neue';">Applying machine learning on large data became part of daily life. Scalability of distributed machine learning algorithms requires tolerance of slower computing nodes referred to as stragglers. To mitigate the effect of stragglers, one can add redundancy to the distributed data. However, stochastic gradient descent (SGD) is known to perform well even when computing on a part of the data. It is shown that for convex loss functions, a small redundancy or no redundancy at all is enough to guarantee good performance of SGD.

yle="margin: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 12px; line-height: normal; font-family: 'Helvetica Neue';">

yle="margin: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 12px; line-height: normal; font-family: 'Helvetica Neue';">In this thesis, we examine the possibility of coding (adding redundancy) over the coordinates rather than coding over the whole data. The goal is to do unequal protection of the coordinates, i.e., give higher protection to the important coordinates that affect the convergence of the algorithm. The goal is to investigate stochastic gradient coordinate descent and check the effect of the redundancy on the convergence. In addition we want to investigate the possibility of ranking the coordinates by importance in order to decide on their unequal protection.

#### Betreuer:

Adaptive SC-like Decoding for Polar and RM codes

Modeling Optical Signal Propagation with a Multi-Modal Nonlinear Schrödinger Equation

## Modeling Optical Signal Propagation with a Multi-Modal Nonlinear Schrödinger Equation

#### Beschreibung

Modeling Optical Signal Propagation with a Multi-Modal Nonlinear Schrödinger Equation

#### Kontakt

#### Betreuer:

Modeling Deterministic and Random Linear Crosstalk in Light Waveguides

Asymmetric Shaping for Higher-Order Modulation Dirty-Paper Coding using Polar Codes

CD Entwickliung (Datenarchitektur) und Datenmodellierung

## CD Entwickliung (Datenarchitektur) und Datenmodellierung

#### Beschreibung

The Common Data Environment is a central data platform that supports all the real estate management related processes from the phase of the inception of a building all the way through the whole lifecycle of it. It is a common data platform for all the participant applications, resources and actors in the real estate portfolio management for the whole BMW Group. A special focus is on the seamless data integration between the planning and the operation phase of the real estate management.

The CDE comprises of a set of integrated data storage modules that are providing data to the consumer applications in an organized and controlled manner. The structure of the CDE is given by it’s architecture and the Real Estate Data Model, this latter being the backbone of the communication between the different applications in the real estate IT landscape. A high level data model already exists in the Real Estate department, and it is already integrated in several business processes.

The scope of the project is to further develop the existing data model, to a higher level of detail and enrich it with new data objects. In the second part of the project the architecture of the CDE has to be established to support the different integration uses cases between the CDE and the satellite applications that are contributing with data or are consuming data from this central environment.

#### Betreuer:

#### Student

List decoding of Interleaved Goppa Codes

## List decoding of Interleaved Goppa Codes

**Stichworte: **

decoding; implementation

#### Beschreibung

Goal: implement a list decoding algorithm for binary interleaved Goppa codes and derive the decoding radius.

Fundalmentals on Goppa codes can be found in [2, Chap 12.3], [3, Chap 2].

Fundalmentals on list decoding can be found in [4, Chap 12], [5, Chap 9].

References:

[1] D. Augot, M. Barbier, and A. Couvreur, “List-decoding of binary goppa codes up to the binary johnson bound,” in 2011 IEEE Information Theory Workshop, pp. 229–233, Oct 2011.

[2] F. J. MacWilliams and N. J. A. Sloane, The theory of error-correcting codes. 1978.

[3] H. Liu, “Decoding of interleaved goppa codes and their applications in code-based cryptosystem,” Master’s thesis, Technical University of Munich, Dec. 2018.

[4] J. Justesen and T. Høholdt, A course in error-correcting codes. Z¨urich: European Mathematical Society (EMS), 2004.

[5] R. M. Roth, Introduction to Coding Theory. Cambridge University Press, 2006.

#### Voraussetzungen

- Channel Coding
- Linear Algebra
- Programming

#### Betreuer:

Private, Secure and Flexible Distributed Machine Learning on the Cloud

## Private, Secure and Flexible Distributed Machine Learning on the Cloud

**Stichworte: **

Distributed machine learning, straggler mitigation, information theoretic privacy and security

**Kurzbeschreibung: **

This project aims at finding coding techniques for implementing machine learning algorithms on untrusted devices on the cloud. A key challenge is to adapt to cloud devices, e.g., IoT, is that have different compute power that change with time.

#### Beschreibung

In the era of big data, running learning algorithms on single computing is becoming a bottleneck. Therefore the need of distributing the computation is inevitable. However, the deployment of distributed computing introduces new challenges that, if ignored, may outweigh the benefit of parallelism.

We consider the master-worker topology in which the master needs to run a computation on its data. The master breaks the computation into smaller tasks distributed to processing nodes referred to as workers. The workers run the tasks in parallel. The master combines the results sent back from the workers to obtain its original computation.

However, heterogeneity of the workers' computation power and/or network link properties can slow down the process for some workers. Waiting for the slowest worker is shown to outweigh the effect of parallelism. Moreover, the privacy of the data is concerned since it is shared with external workers. The leakage of the master data can be harmful or even illegal. The master also risks employing an adversarial computing node as a worker, whose goal is to corrupt the whole computation.

Recently, coding theoretic techniques have been used to speed up the computation, guarantee the privacy and security of the distributed computing paradigm under different settings. The setting of interest for this project is one where the workers have different time-varying compute powers. Thus a flexible coding technique is needed. We focus on matrix-matrix multiplication as a building block in several machine learning algorithms.

In this project, we would like to design codes that allow us to overcome all the three challenges for matrix-matrix multiplication (or more types of computation if the time allows). We start by building on the work in https://arxiv.org/abs/2004.12925. The main focus of the project is on the security of the scheme, i.e., robustness against malicious workers trying to corrupt the computation. We aim to implement the designed codes on Google cloud platform, or Amazon Web Services to test their practicality.

#### Voraussetzungen

Coding Theory

Information Theory

Linear Algebra

Probability Theory

Programming skills

Self-motivation

#### Kontakt

Marvin Xhemrishi: marvin.xhemrishi@tum.de

Rawad Bitar: rawad.bitar@tum.de

#### Betreuer:

Regenerating Codes with Locality

## Regenerating Codes with Locality

#### Beschreibung

Distributed data storage systems need to be able to tolerate the failure of servers without data loss. To maintain this tolerance, newcomers replace failed servers by downloading the required data from the surviving nodes. This repair process can put severe strain on the system and in recent years several coding theoretic measures have been introduced to mitigate this effect. The most promising approaches are codes with locality, where a small number of surviving nodes suffices for repair in most failure events, and regenerating codes, where the amount of data downloaded for repair is minimized.

This thesis will investigate the combination of advanced constructions of codes with locality and regenerating codes, with the goal of designing codes for storage systems that allow for efficient repair with respect to both, the number of servers involved in repair and the the amount of data downloaded.

#### Betreuer:

#### Student

Decoding for High-Throughput Applications

Dynamic Successive Cancellation Flip Decoding of Polar Codes

Product codes with polar component codes

## Product codes with polar component codes

#### Beschreibung

The task of the student would be to implement an iterative decoding of a product code composed of polar component codes. S/he should start by regenerating the results from [1]. Then, the work is extended** to have improved decoding, which still allow for high-throughput applications, for such product codes**. Later, s/he will enhance the code construction tailored to the introduced algoithms to improve the performance. The performance might be compared to the results from [2,3].

[1] https://arxiv.org/pdf/1901.06892.pdf

[2] https://arxiv.org/abs/2008.06938

[3] https://arxiv.org/abs/1908.10397

#### Voraussetzungen

The student

- should have taken the Channel Codes for Iterative Decoding, Information Theory and Channel Coding courses.
- should have some experience with programming and should be eager to implement.

#### Kontakt

mustafa.coskun@tum.de

#### Betreuer:

#### Student

Zero-error capacity for multi-user channels with feedback

Protograph-based LDPC Code Design for Finite Number of Iterations

## Protograph-based LDPC Code Design for Finite Number of Iterations

#### Beschreibung

Low-density parity-check (LDPC) codes are usually designed using an extrinsic information transfer (EXIT) analysis to compute the asymptotic iterative decoding threshold for a given code ensemble. The iterative decoding threshold over an additive white Gaussian noise (AWGN) channel is thereby defined as the minimum signal-to-noise ratio (SNR) for which the a posteriori mutual information converges to one as the number of decoding iterations goes to infinity.

For practical applications, however, decoding is often performed using only a small number of iterations. Mulholland *et al.* investigated a code design for protograph-based LDPC codes where the protograph-based EXIT (PEXIT) analysis [1] is run for the targeted number of decoding iterations only [2]. They showed that for the binary erasure channel (BEC), the obtained *iteration-constrained threshold* does not match the bit error rate (BER) threshold of finite-length codes.

In this thesis, the student will understand and reproduce the results from [2], apply these tools to the AWGN channel, and compare them to code design tools developed at the institute.

[1] G. Liva and M. Chiani, “Protograph LDPC codes design based on EXIT analysis,” in *Proc. IEEE Global Telecommun. Conf. (GLOBECOM)*, Nov. 2007, pp. 3250–3254.

[2] I. P. Mulholland, E. Paolini, and M. F. Flanagan, “Design of protograph-based LDPC code ensembles with fast convergence properties,” in *Proc. Int. ITG Conf. Syst. Commun. Coding (SCC)*, Feb. 2017, pp. 1–6.

#### Voraussetzungen

- Channel codes for iterative decoding

#### Betreuer:

#### Student

### Forschungspraxis oder MSCE Forschungspraxis

Forschungspraxis

Coded Placement in Coded Caching

## Coded Placement in Coded Caching

**Stichworte: **

Coded caching

#### Beschreibung

Coded caching is a study to reduce the transmission delay in broad-/multi-cast by designing the cached data and the transmitting data with coding strategies. There are two phases in coded cahing schemes, placement phase and delivery phase. Coding scheme can be applied in both phase in order to gain in reducing the transmission delay.

#### Voraussetzungen

- Linear Algebra
- Basic Programming
- Channel Coding (Recommended)

#### Kontakt

Hedongliang Liu Doctoral Researcher Technical University of Munich Department of Electrical and Computer Engineering Coding for Communications and Data Storage (COD) Group Theresienstrasse 90 Building N4, Room 3415A D-80333 Munich Phone: +49 89 289 29062 lia.liu@tum.de http://www.lnt.ei.tum.de/en/people/doctoral-researchers/liu/

#### Betreuer:

Adaptive compute strategies for distributed learning

## Adaptive compute strategies for distributed learning

**Stichworte: **

Distributed machine learning, straggler mitigation, adaptive worker selection, adaptive data allocation

**Kurzbeschreibung: **

We consider the master/server computing model. The goal of this project is to design coding techniques that adaptively assigns computational tasks to the workers. In addition, the technique allows the master node to adaptively choose the number of workers it waits for at every iteration. Both assignment strategy and waiting strategy aim to minimize the time spent on running the machine learning algorithm.

#### Beschreibung

We consider the master/server computing model. A master possesses a large amount of data and wants to run a machine learning algorithm on this data. The master offloads the data to several worker machines to parallelize the computation and reduce the time it takes. If the master waits for all the workers, he is limited by the slowest worker. This is known as the straggler problem.

To mitigate the straggler problem, the master can distribute the data with redundancy to the workers. However, adding redundancy to the workers increases the computing time. On the other hand, stochastic gradient descent is known to converge even if the master does not wait for all the workers per iteration. Therefore, a tradeoff between redundancy, and convergence speed arises.

It is shown that for convex loss functions, the master can assign data without redundancy to the workers and chooses the number of workers to wait for per iteration to minimize the waiting time.

The goal of this project is to have the best of both worlds. More precisely, we want to design coding techniques that potentially change the redundancy of the data in an adaptive manner. In addition, the technique allows the master to adaptively choose the number of workers it waits for at every iteration. Both assignment strategy and waiting strategy aim to minimize the time spent on running the machine learning algorithm.

The coding technique we aim to introduce is tailored to the problem at hand. If communication between the master and workers is fast, e.g., serverless compute service, then changing the redundancy is affordable. Otherwise, in settings such as internet of things and edge computing, the master may want to fix the redundancy a priori to a designed value and choose to adaptively wait for a different number of workers per iterations.

It is expected to program a distributed stochastic gradient descent on Google cloud platform, or Amazon Web Services to validate and/or design our system's parameters.

#### Voraussetzungen

Knowledge of coding theory, linear algebra and machine learning

Good programming skills

Self-motivated and eager to learn

Bonus: knowledge of probability theory and convex optimization

#### Kontakt

rawad.bitar@tum.de

https://sites.google.com/site/rawadbitar1

#### Betreuer:

Successive cancellation inactivation decoding of single parity-check product codes (and a non-trivial extension to improve finite-length performance)

## Successive cancellation inactivation decoding of single parity-check product codes (and a non-trivial extension to improve finite-length performance)

#### Beschreibung

The task of the student is to implement an efficient successive cancellation (SC) inactivation decoder for single parity-check product codes, which is (probably) an efficient MAP decoder for such codes over the erasure channels. At the end of the internship, the aim is to assess the MAP performance of very long product codes. Note that this has strong ties with a conjecture that some product codes might be capacity-achieving (although we are just after a numerical evidence for now). If the time permits, we consider the modifications to these codes to enable a better finite-length performance. Related literature is below [1,2].

[1] https://arxiv.org/abs/2004.05969

[2] https://arxiv.org/abs/2008.06938

#### Betreuer:

#### Student

Error-Correction for Partially Stuck Memory Cells

### Ingenieurpraxis

Absicherung des elektrischen Antriebsstranges

## Absicherung des elektrischen Antriebsstranges

#### Beschreibung

.

#### Betreuer:

#### Student

Random Fraction Placement in Coded Caching

## Random Fraction Placement in Coded Caching

**Stichworte: **

Coded caching; Index Coding

#### Beschreibung

In some communication systems end users are equiped with storages, the communication load during the peak hours can be reduced by having users pre-fetch part of the content during the scilent hours. Coded caching is a study to design the pre-fetching without the knowledge of users demands and the delivery scheme based on the users caches. However, many current schemes are facing the subpacketization problem in order to achieve the optimal load.

#### Voraussetzungen

- Basic programming

#### Betreuer:

Erweiterung der Agabiz App um eine automatisierte Standort-Ermittlung und Fahrtzeitkontrolle mit Hilfe von iBeacon-/Bluetooth-Technologie

Umsetzung einer frequenzselektiven IQ-Imbalanz Korrektur für OFDM Direct Conversion Receiver

translation of coded modulation library from Matlab/C into julia

## translation of coded modulation library from Matlab/C into julia

**Stichworte: **

Matlab, C, C++, julia

**Kurzbeschreibung: **

It is the students task to translate function from MATLAB and C into julia language.

#### Beschreibung

the students should translate functions from Matlab and C to julia. the functions involve calculation of infomation theoretic quantities to basic function of a discrete time transmission chain.

The students task is to learn julia and matlab to a extend that the translation from one to the other language is possible. We furthermore expect the student to learn how to use git and gitlab for managing larger projects.

#### Voraussetzungen

basic programming knowledge