https://www.um.edu.mt/library/oar/handle/123456789/10954 Thu, 09 Apr 2026 11:07:11 GMT 2026-04-09T11:07:11Z https://www.um.edu.mt/library/oar/handle/123456789/145391 Title: Radio system architecture for a UHF frequency-multiplexed phased-array pico-satellite ground station Abstract: Recent years have seen a surge in low-Earth-orbit (LEO) small-satellite activity along with a corresponding demand for agile, low-cost ground stations (GSs). Building on this momentum, the University of Malta’s (UM) satellite efforts through the Astrionics Research Group’s ASTREA project aim to conduct in-orbit validation, including testing of materials and electronic components. Drawing on these efforts, this dissertation surveys a frequency-multiplexed phased-array (FMPA) GS for ultra-high-frequency (UHF) P-band satellite links, targeting affordability by using commercial off-the-shelf (COTS) components. To date, more than one thousand five hundred nano-satellites operate in the UHF band, remaining the most utilised choice for launched operations. Presently, the GS configuration requires sixty-four coaxial cable runs beneath the icosahedral geodesic-dome phased-array antenna (GDPAA). Frequency-division multiplexing (FDM) in the FMPA architecture collapses these to two, enabling a compact GS stack with a full complement of usable antenna elements (AEs) and reduced maintenance effort. This study frames and evaluates five candidate architectures, then shortlists two that apply AE-level phasing for beamforming and beam steering, either in software or hardware, culminating in a system (HardwarePS1) enabling multibeam, bidirectional operation. At the target 435 MHz, results confirm feasibility by exceeding ASTREA mission requirements, with the uplink budget yielding a 14.2 dB margin using two GDPAA planar faces, and the downlink achieves −124.9 dBm noise floor through a cascaded noise figure (NF) equivalent to approximately 576 K system noise temperature, delivering a 6.2 dB link margin. End-to-end MATLAB Simulink RF Blockset simulations, including device nonidealities across both signal chains and a 290 K thermal white-noise model, corroborate the operating point to nearly −59 dBc at the desired frequency. From a cost perspective, the baseline bill of materials (BoM) costs roughly €10,500, excluding printed circuit board (PCB) fabrication, while still maintaining the low-cost objective relative to phased-array alternatives. Finally, this work proposes the first reported FMPA uplink and end-to-end UHF operation with hardware-based phasing, indicating a credible, scalable path to multi-satellite GS operations aligned with contemporary LEO mission payloads. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/145391 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145390 Title: Sequential decoding of convolutional codes under insertion and deletion errors Abstract: Synchronisation errors pose a major challenge to classical error-correcting decoding algorithms, which typically assume perfect alignment between transmitted and received sequences. Such errors arise in modern communication and storage systems, including packet-based networks and DNA-based storage where maintaining symbol synchronisation cannot be guaranteed. This dissertation addresses this challenge by implementing a Stack sequential decoder tailored for the Binary Substitution, Insertion and Deletion (BSID) channel and by integrating it as a new module within the SimCommSys simulation framework. The decoder works with convolutional codes and incorporates three path-metric formulations drawn from literature: a joint-distribution based metric; a conditional probability based metric and a weighted Levenshtein distance (WLD) based metric, allowing a unified comparison of their performance under synchronisation errors. Simulation results confirm that the implemented decoder operates correctly across a wide range of error conditions and convolutional codes. The implementation matches or closely replicates reference results from literature, validating the correctness of the metrics and the decoding logic. Among the three metrics, the joint-distribution based metric demonstrated the most robust overall performance after a detailed comparison of decoding performance and complexity with different convolutional codes. Overall, this work provides both a practical contribution with a fully functional sequential decoder for synchronisation errors and a comparative study that clarifies the strengths of three different metric formulations. The decoder serves as a foundation for future developments and research in sequential decoding under synchronisation errors. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/145390 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/145389 Title: Empirical evaluation of RaptorQ codes for multicast video streaming over IEEE 802.11ac wireless LANs Abstract: In this dissertation, RaptorQ fountain codes are used to provide reliable video multicasting over IEEE 802.11ac Wi-Fi networks. Even though multicasting is efficient because of its one-to-many video delivery, it results in high packet loss since it offers no acknowledgement or retransmission mechanisms. The aim of this dissertation is to design, implement, and evaluate a complete testbed that integrates video encoding, RaptorQ forward error correction (FEC), Wi-Fi multicast transmission, decoding, and playback. The system combines FFmpeg, RaptorQ encoder and decoder and FFplay into a reproducible end-to-end pipeline. Three RaptorQ configurations were tested, where the number of source symbols K was fixed at 100 and the number of repair symbols H was varied between 0, 50, and 100. The testing was done at the University of Malta faculty of ICT Auditorium, where three different positions were tested. Reliability at packet and block levels, video quality, transmission rate, and end-to-end delay were evaluated through Symbol Error Rate (SER), Block Error Rate (BLER), Mean Square Error (MSE), and the end-to-end delay measurements. When no repair symbols were used, the multicast transmission suffered from large losses with an SER of approximately 1.05%-1.7% and a BLER of approximately 14%-56%. When 50 repair symbols were used, 72%-89% of the symbol losses were recovered, with SER ranging from 0.13%-0.25% and BLER ranging from 0.29%-0.52%. With 100 repair symbols, near-perfect recovery was achieved, with SER ranging from 0.045%-0.16% and BLER from 0.075%-0.24%. Video quality improved as the average MSE dropped from 300-900 (severe degradation) to 1.6-6.6 (nearly lossless). The end-to-end delay remained below the 0.5-1s threshold defined for the auditorium scenario across all configurations. These results confirm that RaptorQ can drastically improve the reliability of Wi-Fi video multicasting because both packet-level reliability and visual quality significantly improved with minimal delay. The implemented testbed serves as a reusable framework for future research on video protected by FEC streamed over wireless networks. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/145389 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/140266 Title: Real-time multi-camera tracking and od-matrix estimation of vehicles Abstract: With computer vision, it is possible to capture data which is of great use to urban planners and infrastructure engineers. Informed decisions can then be taken to evolve existing and new infrastructure in a more robust and greener way. Data can be captured with the use of a single-camera tracker, which detects and tracks vehicles and pedestrians in the camera view. However, in more complex scenarios, such as a roundabout or intersection, the use of a single camera is not sufficient. For this study, a single-camera tracker, developed by Greenroads Ltd, is readily available [...] Description: M.Sc. ICT(Melit.) Mon, 01 Jan 2024 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/140266 2024-01-01T00:00:00Z