1,212 research outputs found
Hardware Architecture of a QAM Receiver for Short-Range Optical Communications
[EN] Short-reach optical fiber communications systems aim to achieve high throughput, in the order of tens of Gbps. The implementation of these high-speed systems requires parallel processing, which makes low-complexity designs of their subsystems a key to the successful large-scale deployment of this technology. Half-Cycle Nyquist Subcarrier Modulation (HC-SCM) was originally suggested for these systems with the goal of using as much bandwidth as possible and, therefore, achieving high communication rates. Recently, Oversampled Subcarrier Modulation (OVS-SCM) was proposed as an alternative more computational efficient than HC-SCM and also with a better spectral efficiency. This paper proposes a hardware-efficient architecture for an OVS-SCM receiver, which takes into account the inherent parallel processing of these systems. This receiver takes 16 samples in parallel from a 5 GSa/s analog-to-digital converter with a 3.2 GHz 3 dB bandwidth. Design solutions for the frame detection block, the mixer, the resampler, the fractional interpolator, the matched filter and the timing estimator are presented. Our results show that, compared to the HC-SCM receiver, this proposal reduces the computational load of the downconverter stages by 90%. FPGA implementation results are given to demonstrate that our proposal can be implemented in state-of-the-art devices.This work was supported in part by MCIN/AEI/10.13039/501100011033 under Grants RTI2018-101658-B100 and PID2021-126514OB-I00, and in part by the European Union through "ERDF Away of making Europe."Valls Coquillat, J.; Torres Carot, V.; Pérez Pascual, MA.; Almenar Terre, V. (2023). Hardware Architecture of a QAM Receiver for Short-Range Optical Communications. Journal of Lightwave Technology. 41(2):451-461. https://doi.org/10.1109/JLT.2022.321735745146141
University of Windsor Graduate Calendar 2023 Spring
https://scholar.uwindsor.ca/universitywindsorgraduatecalendars/1027/thumbnail.jp
Stokes Vector Modulation of Optical Signals; Coherence, Noise, and Digital Signal Processing
Stokes vector modulation (SVM) is a method of encoding information onto an optical wave by controlling its amplitude and its state of polarization (SOP). SVM offers the potential to achieve the high spectral efficiency of multi-dimensional symbols using a power-efficient, direct-detection receiver. Combining the two independent degrees of freedom representing polarization with one representing amplitude, SVM symbols are defined in a 3-D space of Stokes vectors, where vector length represents the amplitude and altitude/azimuth angles represent the SOP. The recoverable information content is fundamentally limited by the noise on the received signal, which may include shot noise due to photon-counting, electrical circuit noise, amplified spontaneous emission due to optical amplifiers, and self-interference of low-coherence light sources. Some of these noise terms do not obey the usual approximation of additive white Gaussian noise, and some may not be isotropic in Stokes space.
Taking these complexities into account, I will theoretically analyze and compare several recently-proposed SVM receiver designs under different conditions of source coherence and channel impairments. For the most promising options, I will design symbol constellations and receiver decision strategies suitable for maximal data throughput. Construction and operation of apparatus to experimentally verify bit-error performance up to at least 10 Gsym/s with different sources, constellations, fiber spans, and receivers will be an essential component of the work. Possible extensions may include simultaneous modulation of the degree of polarization, to create a 4-D symbol space.
Further, I will develop and characterize a system based on a cubic constellation for 8-SVM, using an off-the-shelf integrated modulator driven with simple bias points and data waveforms. Symbol error rates (SER) and bit error rates BER) are measured up to 30 Gb/s, and analysis of the symbol errors reveals a significant effect of inter-symbol interference.
Finally, I will theoretically and experimentally demonstrate a novel adaptation of independent component analysis (ICA) for compensation of both cross-polarization and inter-symbol interference in a direct-detection link using Stokes vector modulation (SVM). SVM systems suffer from multiple simultaneous impairments that can be difficult to resolve with conventional optical channel DSP techniques. The proposed method is based on a six-dimensional adaptation of ICA that simultaneously derotates the SVM constellation, corrects distortion of constellation shape, and mitigates inter-symbol interference (ISI) at high symbol rates. Experimental results at 7.5 Gb/s and 15Gb/s show that the newly-developed ICA-based equalizer achieves power penalties below ~1 dB, compared to the ideal theoretical bit-error rate (BER) curves. At 30-Gb/s, where ISI is more severe, ICA still enables polarization de-rotation and BE
Rate-splitting multiple access for non-terrestrial communication and sensing networks
Rate-splitting multiple access (RSMA) has emerged as a powerful and flexible
non-orthogonal transmission, multiple access (MA) and interference management
scheme for future wireless networks. This thesis is concerned with the application of
RSMA to non-terrestrial communication and sensing networks. Various scenarios
and algorithms are presented and evaluated.
First, we investigate a novel multigroup/multibeam multicast beamforming strategy
based on RSMA in both terrestrial multigroup multicast and multibeam satellite
systems with imperfect channel state information at the transmitter (CSIT). The
max-min fairness (MMF)-degree of freedom (DoF) of RSMA is derived and shown
to provide gains compared with the conventional strategy. The MMF beamforming
optimization problem is formulated and solved using the weighted minimum mean
square error (WMMSE) algorithm. Physical layer design and link-level simulations
are also investigated. RSMA is demonstrated to be very promising for multigroup
multicast and multibeam satellite systems taking into account CSIT uncertainty
and practical challenges in multibeam satellite systems.
Next, we extend the scope of research from multibeam satellite systems to satellite-
terrestrial integrated networks (STINs). Two RSMA-based STIN schemes are
investigated, namely the coordinated scheme relying on CSI sharing and the co-
operative scheme relying on CSI and data sharing. Joint beamforming algorithms
are proposed based on the successive convex approximation (SCA) approach to
optimize the beamforming to achieve MMF amongst all users. The effectiveness and
robustness of the proposed RSMA schemes for STINs are demonstrated.
Finally, we consider RSMA for a multi-antenna integrated sensing and communications (ISAC) system, which simultaneously serves multiple communication users
and estimates the parameters of a moving target. Simulation results demonstrate
that RSMA is beneficial to both terrestrial and multibeam satellite ISAC systems by
evaluating the trade-off between communication MMF rate and sensing Cramer-Rao
bound (CRB).Open Acces
University of Windsor Graduate Calendar 2023 Winter
https://scholar.uwindsor.ca/universitywindsorgraduatecalendars/1026/thumbnail.jp
Timbral Analysis and Recording Parameter Transformations of Snare Drums
A snare drum is capable of producing a wide range of timbres influenced by playing technique, its physical construction, and the recording methods used. When a recording engineer configures drums and studio equipment, they adjust a plethora of real-world recording parameters to achieve the desired timbre. These recording parameters impart their own timbral properties by varying amounts, and in most cases the only way to modify these properties is to re-record the audio with changes applied to the real-world variables.
This thesis examines methods for computational transformations of snare drum recordings to elicit perceptual changes that mimic modification of real-world recording variables. This is achieved through four main investigations, presented throughout this thesis, two which cover timbral analysis of snare drum recordings, and two which explore post-hoc recording parameter transformations.
Strike velocity and microphone selection are factors known to affect snare drum timbre, the first study analyses timbral differences associated with snare drum strike velocity. Results show that listeners are able to distinguish between high and low velocity strikes using timbral cues alone, with microphone selection having no influence on this perceptual identification. Audio analysis reveals distinct temporal and spectral features, with higher velocity strikes producing greater energy in the lower mid-range and significantly longer decay times. The second study aims to demystify the subjective preference of different microphones for snare drum recording. For the majority of microphones, preference does not change between isolated strikes and those with the presence of bleed from the hi-hat and kick drum. On average, preference is higher for condenser microphones compared to dynamic. Additionally, spectral centroid and an objective measure of brightness positively correlate with subjective scores.
The ability to perceptually modify drum recording parameters in a post-recording process would be of great benefit to engineers limited by time or equipment. The first post-hoc recording parameter transformation study focuses on microphone selection, mapping the spectral features from highly-preferred microphones onto a microphone with less favourable timbral characteristics. This investigation also details the development and evaluation of a robotic drum arm for consistent strike velocity. Subjective assessment reveals that participants show no preferences between recordings from highly-preferred microphones and those from a transformed least-preferred microphone. The last study employs a data-driven approach for post-recording modification of dampening and microphone position. The system consists of a autoencoder that analyses an audio input and predicts optimal parameters of one or more third-party audio effects, which process the audio to produce the desired transformations. Two novel audio effects are proposed and compared against existing audio plugins. Perceptual quality of transformations is assessed through a subjective listening test and an object evaluation is used to measure system performance, positive results demonstrate a capacity to emulate snare dampening
Single-Frequency Network Terrestrial Broadcasting with 5GNR Numerology
L'abstract è presente nell'allegato / the abstract is in the attachmen
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