September 2021 - Kommunikationstechnik-Kolloquium

Communication Technology Colloquium at IKS
by Irina Ronkartz 17 Sep '21

17 Sep '21

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium at IKS. *Friday, September 24, 2021* *Speaker:* Frederik Blang *T**ime:* 2:00 p.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Lecture*: Speech Enhancement for Active Occlusion Cancellation on Noisy Environments The natural perception of one's own voice while wearing a headset is increasingly in the focus of customers and manufacturers. Due to the occlusion effect which occurs when the ear canal is blocked, body-conducted sound is amplified, resulting in an unpleasant sound of the own voice. It becomes difficult to control the volume of one's own voice leading to earlier vocal fatigue. Active Occlusion Cancellation (AOC) aims to suppress this effect and can be combined with a hear-through system for a natural own-voice perception. In noisy environments, for example call centers, it is desirable to only equalize the own voice. Some business headsets already provide a sidetone which uses a boom microphone to record the own voice, however this signal often isn't equalized. This thesis develops a real-time system which provides a natural own-voice perception for the user of a headset using the boom microphone. Besides the implementation of a filter for the direct sound, also the room reverberation of one's own voice is estimated using convolution. Algorithmic room simulation on a DSP is considered, but ultimately rejected due to memory card. The low-latency filtering of the direct sound is performed on the DSP, while the longer room filters are run on the PC. Evaluations using simulations and measurements show the direct-path filter to perform well, while the room filters can't provide a natural estimation of the room sound. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 09 Sep '21

09 Sep '21

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Thursday, September 16, 2021* *Speaker:* Vlerar Shala *Time:* 11:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Lecture*: AI-Based Optimization of Pulse Shaped OTFS for Vehicular Communication Future vehicular communication systems require a reliable communication to enable connected and automated driving. Vehicular channels are considered to be truly doubly-dispersive channels, i.e., strongly varying in both time and frequency. However, the performance of the traditional wireless communication systems operating under doubly-dispersive channels degrades significantly. Orthogonal time frequency and space (OTFS) is a recently proposed modulation scheme designed to be robust against doubly-dispersive channels. OTFS is a new and novel two-dimensional (2D) pulse-shaped modulation scheme designed in the delay-Doppler (DD) domain and promises significant improvements on the physical layer. OTFS is a combination of classical Gabor signaling with a unique time-frequency (TF) spreading. Data symbols are located in the DD domain and spread over the entire TF domain using the symplectic finite Fourier transform (SFFT). The TF spreading accounts in a linear fashion for the doubly dispersive nature of time-variant multi-path channel. The TF spreading is also referred to as OTFS transform and the Gabor transform as the Heisenberg transform. However, OTFS requires proper channel information and the use of appropriated equalizers to exploit the full spreading gain. Doubly-dispersive channels are characterized by their spreading region spanned by two times max, and max, corresponding to the maximum Doppler shift and delay spread. To mitigate the strong interference between different TF slots, TF grid and pulses should “match” the DD spreading region of the doubly-dispersive channel, typically determined on a longer time scale-like. This approach is known as pulse and grid matching rule. In this thesis, we use the so-called mobility modes with distinct grid and pulses to follow the pulse and grid matching rule. However, mobility modes control the interference on a coarse level because they cannot match the pulse and grid matching rule completely. The remaining interference is accounted by the implemented mean square error (MMSE) linear equalizer, which is tuned for each frame. We implement the OTFS transceiver based on a polyphase implementation for orthogonalized Gaussian pulses and evaluate mobility modes with doubly-dispersive vehicular channels generated by the QuaDRiGa channel simulator. For practical implementation, the performance of mobility modes should be predicted and then the mobility mode with the best performance is selected to send the next frame. However, the prediction of mobility modes requires the prediction of the channel itself. In this thesis, we propose a novel method to predict the channel by predicting the spreading function which represents the channel in the DD domain. We propose to predict the spreading function using a new variant of Long Short-Term Memory (LSTM) neural networks known as Convolutional LSTM. The architecture of Convolutional LSTM is both recurrent and convolutional which enables it to capture the spatiotemporal correlation of the data and utilize it for the prediction. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at: http://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 02 Sep '21

02 Sep '21

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquiums. *Friday, September 10, 2021* *Speaker:* Rocio Martin Lima *Time:* 11:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master Lecture:* Optimized Receiver Systems Preserving Maximum Relevant Mutual Information In modern communication systems the receiver-sided signal processing often results in bottlenecks. In particular, high-speed computations in channel decoders are demanding, but also crucial to achieve high data rates. Therefore, reduced complexity decoding algorithms for the widely used low-density parity-check (LDPC) codes are developed in this thesis. State-of-the-art LDPC decoders use costly mathematical operations and high-precision log-likelihood ratios in iterative message passing algorithms. Both typically results in high decoder complexity. In contrast, this thesis proposes to design check node operations that decode directly using the bit-level representation of strongly quantized integer messages. Like this, small logical circuits that only use simple bit-level operations (e.g. XOR) on the passed messages can replace demanding check node operations. At the same time, only a small number of bits per message is required. An information bottleneck inspired design method is applied to learn suitable logical circuits for decoding. This method involves genetic optimization algorithms. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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