| 1. |
- Browne Mwakyanjala, Moses, 1986-
(författare)
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A Software-Defined Baseband for Satellite Ground Operations : Feasibility and Design
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Satellite telemetry, tracking, and command (TT&C) is a crucial activity needed to maintainthe health of a spacecraft or sometimes to facilitate payload data download. TT&Cground operations are facilitated by a communication device known in the TT&C communityas a baseband. State-of-the-art baseband systems currently in the market haveseveral financial and technical limitations. Financial drawbacks include high capital expenditure,operational expenditure, maintenance costs, and high upgrade costs, whiletechnical limitations include both upgradability and scalability.This thesis presents the feasibility study of a software-defined baseband (SDB) as aviable alternative to existing basebands. The SDB considered here is implemented on aradio architecture that consists of a general-purpose processor for performing radio functionsand low-cost commercial-off-the-shelf, software-defined radio frontends for signalsampling. The research questions focus on the feasibility and design aspects of this SDB.This thesis approaches the design of the SDB with a software development cyclethat involves functional analysis (design), verification, and validation of the radio functionsconstituting the SDB system. The radio functions are the telemetry receiver andthe telecommand transmitter. Functional analysis is performed through functional flowblock diagrams. The verification process is performed through simulations that take intoaccount realistic channel impairments for missions operating in the S-band and characterizedby the Consultative Committee for Space Data Systems (CCSDS) as category Amissions (less than 2 million km). Validation is performed on a laboratory testbed andseveral orbiting satellites.Through the above software development cycle, the telemetry receiver and telecommandtransmitter are developed using the open-source GNU radio development kit. Modulationschemes, line codes, and filters along with CCSDS forward error correction codescommonly employed in TT&C communications are successfully designed, verified in simulations,and validated in a hardware testbed. The performance results from the validationtests demonstrate that it is feasible to implement the SDB TT&C radio functions on theadopted radio architecture.Finally, this thesis investigates in detail the novel concept of multiple spacecraft peraperture (MSPA) that enables communication with several spacecraft from a single antenna.It focuses on in-band interference and out-of-band emissions arising from radiatingmultiple telecommand links from a low-cost SDR frontend. An MSPA transceiver is successfullydeveloped and integrated into the SDB system. Validation tests show that itis feasible for the integrated MSPA transceiver to radiate two telecommand links whileconforming to spectral regulations.
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| 2. |
- Browne Mwakyanjala, Moses, et al.
(författare)
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Feasibility of using a software-defined baseband for multiple space per aperture (MSPA) ground operations
- 2022
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Ingår i: International Journal of Satellite Communications And Networking. - : John Wiley & Sons. - 1542-0973 .- 1542-0981. ; 40:2, s. 133-147
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the feasibility of performing multiple spacecraft per aperture (MSPA) ground operations by using a low-cost software-defined baseband (SDB). The SDB is a Consultative Committee for Space Data Systems (CCSDS)-compliant baseband that employs a personal computer for signal processing and a low-cost commercial-off-the-shelf RF front end for RF signal sampling. The SDB is customized to offer traditional telemetry, tracking, and command (TT&C) services for near-Earth missions operating in S band. The study starts by reviewing MSPA methods already studied by space agencies such as NASA and ESA before going to MSPA methods proposed in the latest CCSDS blue book on RF and modulation systems. The feasibility of operating the CCSDS-proposed multiple uplink carrier MSPA method using the SDB is assessed after evaluating in-band interference and out-of-band emissions from the uplink signals radiated by the low-cost RF front end employed by the SDB. Furthermore, we present a case study where the SDB is used in MSPA operations on a typical solid-state amplifier (SSPA) amplifier typically used in near-Earth missions.
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| 3. |
- Browne Mwakyanjala, Moses, et al.
(författare)
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Validation of a software-defined baseband system for satellite telemetry and telecommand
- 2021
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Ingår i: International Journal of Satellite Communications And Networking. - : John Wiley & Sons. - 1542-0973 .- 1542-0981. ; 39:6, s. 605-625
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the validation of a software-defined baseband (SDB) system for satellite telemetry and telecommand (TM/TC). The baseband system was developed using the open-source GNU Radio development kit. It runs on a personal computer connected to a commercial-off-the-shelf (CoTS) RF frontend. The validation process was performed by the use of a mission-qualified satellite emulator, a state-of-the-art baseband unit, and orbiting satellites. The baseband is designed to offer multimission support. Hence, it includes a suite of modulation schemes, line codes, matched filters, and Consultative Committee for Space Data Systems (CCSDS) forward error correction codes (convolutional, Reed–Solomon, concatenated, and low-density parity-check [LDPC]) typically employed in TM/TC missions. The figures of merit used for the validation of the TM receiver are bit error rate (BER) and frame error rate (FER). For the TC transmitter, the validated features are modulation index, power spectrum, and the physical layer operations procedures (PLOP).
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| 4. |
- van de Beek, Jaap, et al.
(författare)
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REM-enabled opportunistic LTE in the TV band
- 2012
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Ingår i: 2012 IEEE International Symposium on Dynamic Spectrum Access Networks (DYSPAN 2012). - Piscataway, NJ : IEEE Communications Society. - 9781467344470 ; , s. 272-273
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Konferensbidrag (refereegranskat)abstract
- In this demonstration paper we describe a prototype of an LTE system deployment that opportunistically exploits the spectral white spaces in the upper UHF TV bands, intelligently guided in its spectum access by a radio environment map (REM). The architecture is modular in the sense that interfaces are generic and minimal. In the proposed demo we will illustrate how information of primary transmitters and other secondary transmitters as well as estimates of the radio field strength over frequency, time and space can be made available and exploited by a secondary TDD-LTE base station to make judicious decisions on its spectral occupation.
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| 5. |
- Ashraf, Asra, et al.
(författare)
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Enabling High-speed Ultrasound Communication Through Thin Plates by Reverberation Suppression
- 2021
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Ingår i: 2021 IEEE International Ultrasonics Symposium (IUS). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- In all digital communications, knowledge of the propagation channel between the transmitter and the receiver is essential. For transmitting of data through solid bodies, such as metal plates, pipe walls, etc., ultrasound is a viable alternative to radio communication and wired transmission. In ultrasound communication, the channel consists of two parts, the combined response of the transducers used as transmitter and receiver, and the impulse response of the propagation medium itself. For a thin plate with parallel surfaces, this results in a reverberating channel that significantly reduces the achievable bitrate if not handled properly. In this paper we show with simulations how the bit-error rate in Orthogonal Frequency Division Multiplexing (OFDM) communications, is affected by the reverberating nature of the plate, and how this can be overcome by the introduction of a channel shortening filter placed in front of the OFDM conventional receiver. The results show that this significantly reduces the bit-error rate, especially for thin plates. If the reverberations instead were to be compensated by the conventional channel equalization method in OFDM, we show that for the example in the simulations, the bitrate would drop by almost 25 %, from about 3.9 Mbit/s to about 2.9 Mbit/s.
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| 6. |
- Ashraf, Asra, 1989-, et al.
(författare)
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The solid-body reverberating ultrasound communications channel and its OFDM interference
- 2022
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Ingår i: 2022 IEEE Latin-American Conference on Communications (LATINCOM). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- In this paper we present an analytical approach to the solid-state ultrasound communications channel. Channel reverberations and the long associated channel delay spreads pose the possibility that the channel length exceeds that of the moderate cyclic prefix in an orthogonal frequency division multiplexing (OFDM) system, resulting in intersymbol and intercarrier interference. We present a channel model based on the propagation material characteristics and evaluate the extent and impact of the intrinsic OFDM interferences. We derive an analytical expression and show with simulations that the intersymbol and intercarrier interference (ISI and ICI) are spectrally concentrated to the lower frequencies of the OFDM multiplex.
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| 7. |
- Ashraf, Asra, et al.
(författare)
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Ultrasound Communication Through Thin Plates: Understanding and Estimating the Channel
- 2022
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Ingår i: 2022 IEEE International Ultrasonics Symposium (IUS). - : IEEE. - 9781665466578
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Konferensbidrag (refereegranskat)abstract
- As with all digital communications, understanding the propagation channel is essential. In this paper we present an analytical model of a channel consisting of a thin plate, including effects of frequency-dependent speed of sound and attenuation. We show how a compressed sensing approach can be used to estimate this channel impulse response from real measurements, even for cases when the plate thickness causes the reverberating pulses to overlap. The estimate can be seen as a sparsity constrained deconvolution of the combined impulse responses of the transmitting and receiving transducers. We then show with simulations that the proposed sparsity-constrained estimate is able to cope also in the presence of dispersion. We also analyze the performance of the proposed method both with simulations and experiments on 6 mm and 2 mm thick glass plate and 3 mm thick aluminum plate, and our results show that the model assumptions seems to hold.
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| 8. |
- Ashraf, Asra, 1989-
(författare)
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Ultrasound Communication through Thin Plates: Understanding the Channel
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ultrasound, composed of sound waves with frequencies above the human audible range, has become widely used in various technological fields for digital communications. In the past, acoustic and ultrasonic waves were employed in military and commercial un-derwater wireless communication systems due to their superior performance compared to electromagnetic waves. Ultrasound has also emerged as a viable alternative to radio and wired transmission for data transmission through solid bodies like metal plates and pipe walls. Notably, ultrasound offers high-security features as it is nearly undetectable from outside the room, minimizing the risks of wireless interception and attacks like Bluesniping and jamming.In any digital communication system, understanding the propagation channel between the transmitter and receiver is crucial. The ultrasound communication channel comprises three main components: transmitting and receiving transducers and the medium through which the sound propagates. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier scheme that divides the available spectrum into multiple non-overlapping subcarriers for digital communication.In the context of ultrasound communication, the channel consists of two parts: the combined response of the transducers used as the transmitter and receiver, and the im-pulse response of the propagation medium. When dealing with a thin plate with parallel surfaces, this results in a reverberating channel. The reverberating channel comprises a primary pulse along with echo pulses that possess similar shapes but decaying amplitudes. The amplitude decay occurs due to four prominent factors: power losses in the trans-ducers at each side, transmission losses at the boundaries of the plate and transducer, ultrasound pulse attenuation within the plate, and beam spreading as the ultrasound pulse travels over distance. The reverberations elongate the impulse response of the channel, thus require a long cyclic prefix to prevent data symbols to overlap. However, this limitation restricts the achievable bit rate and energy efficiency of the system.In this thesis, we present a model for the reverberating ultrasound channel suitable for various plate materials. We propose a novel system-level path loss model that accounts for losses at the transducers, transmission losses, material attenuation, and diffraction losses. Based on this model, we calculate a comprehensive link budget that explicitly considers plate thickness. Furthermore, we conduct a quantitative analysis to evaluate the impact of Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) on the performance of the OFDM system. Through computer simulations, we evaluate the system’s performance and demonstrate that for a metal plate with a thickness of 5 mm, an uncoded data rate of 32 Mbps can be achieved.
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| 9. |
- Atanasovski, Vladimir M., et al.
(författare)
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Constructing radio environment maps with heterogeneous spectrum sensors
- 2011
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Ingår i: 2011 IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2011). - Piscataway, NJ : IEEE Communications Society. - 9781457701771 ; , s. 660-661
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Konferensbidrag (refereegranskat)abstract
- In this demonstration proposal we describe a prototype of a radio environment map (REM) for storing and reasoning about spectrum data obtained from heterogeneous sources. The architecture of the REM prototype is both modular and extendible, and can be used with very diverse spectrum sensors, ranging from high-fidelity spectrum analyzers to dedicated low-cost embedded solutions. In the proposed demonstration we will illustrate how information such as transmitter locations and estimates of spectrum occupancy over space and time can be inferred and made available through the REM, based on information obtained from a network of different spectrum sensors deployed specifically for the demonstration
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| 10. |
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