Alongside the various projects, owe are carrying out research in the fields of:
Software Defined Radio, Cognitive Radio, RF-SoC, Cellular Networks, OpenRAN, Shared Spectrum and Dynamic Spectrum Access
A list of recent publications is provided below, with links to open access copies of the work.
Rapid Prototyping and Validation of FS-FBMC Dynamic Spectrum Radio with Simulink and ZynqSDR
Kenneth W. Barlee, Robert W. Stewart, Louise H. Crockett, Neil C. MacEwen
IEEE Open Journal of the Communications Society, Nov 2020
Abstract — This paper presents the research carried out in developing and targeting a novel real-time Dynamic Spectrum Access (DSA) Frequency Spread Filter Bank Multicarrier (FS-FBMC) transmitter prototype to programmable ‘ZynqSDR’ Software Defined Radio (SDR) hardware, and introduces a series of experiments used to validate the design’s ‘cognitive’ DSA capabilities. This transmitter is a proof of concept, that uses DSA techniques to enable Secondary Users (SUs) to access the band traditionally used for FM Radio broadcasting (88-108 MHz), and establish data communication channels in vacant parts of the FM Radio Primary User (PU) spectrum using a multicarrier modulation scheme with a Non Contiguous (NC) channel mask. Once implemented on the hardware, the transmitter is subjected to various FM Radio environments sampled from around Central Scotland, and it is demonstrated that it can dynamically adapt its NC transmitter mask in real time to protect the FM Radio signals it detects. A video is presented of this dynamic on-hardware spectral reconfiguration, and the reader is encouraged to view the video to appreciate the responsiveness of the design. An investigation into potential FBMC guardband sizes is carried out, with initial findings indicating a guardband of 200 kHz (either side of an FM Radio station) is required in order to prevent interference with the PUs. This paper also demonstrates the capabilities of the MATLAB and Simulink Model Based Design Zynq-Based Radio workflow, and provides a case study and reference design that we feel other researchers working in this field can benefit from.
Control and Visualisation of a Software Defined Radio System on the Xilinx RFSoC Platform Using the PYNQ Framework
Josh Goldsmith, Craig Ramsay, David Northcote, Kenneth W. Barlee, Louise H. Crockett, Robert W. Stewart
IEEE Access, July 2020
Abstract — The availability of commercial Radio Frequency System on Chip (RFSoC) devices brings new possibilities for implementing Software Defined Radio (SDR) systems. Such systems are of increasing interest given the pace of innovation in wireless technology, and the pressure on RF spectrum resources, leading to a growing need to access the spectrum in more dynamic and innovative ways. In this paper, we present an SDR demonstration system based on the Xilinx RFSoC platform, which leverages the Python-based `PYNQ’ (Python Productivity for Zynq) software framework. In doing so, we highlight features that can be extremely useful for prototyping radio system design. Notably, our developed system features Python-based control of hardware processing blocks and Radio Frequency (RF) data converters, as well as direct visualisation of communications signals captured within the chip. The system architecture is reviewed, hardware and software components are discussed, functionality is demonstrated, and aspects of the system’s performance are evaluated. Finally, it is noted that this combined RFSoC + PYNQ approach is readily extensible for other SDR systems; we highlight our online shared resources, and invite other engineers to investigate and build upon our work.
Generic Compression of Off-The-Air Radio Frequency Signals with Grouped-Bin FFT Quantisation
Damien Muir, Louise H. Crockett, Robert W. Stewart
Abstract — This paper studies the capabilities of a proposed lossy, grouped-bin FFT quantisation compression method for targeting Off-The-Air (OTA) Radio Frequency (RF) signals. The bins within a 512-point Fast Fourier Transform (FFT) are split into groups of adjacent bins, and these groups are each quantised separately. Additional compression can be achieved by setting groups which are not deemed to contain significant information to zero, based on a pre-defined minimum magnitude threshold. In this paper, we propose two alternative methods for quantising the remaining groups. The first of these, Groupedbin FFT Threshold Quantisation (GFTQ), involves allocating quantisation wordlengths based on several pre-defined magnitude thresholds. The second, Grouped-bin FFT Error Quantisation (GFEQ), involves incrementing the quantisation wordlength for each group until the calculated quantisation error falls below a minimum error threshold. Both algorithms were tested for a variety of signal types, including Digital Private Mobile Radio 446 MHz (dPMR446), which was considered as a case study. While GFTQ allowed for higher Compression Ratios (CR), the compression process resulted in added quantisation noise. The GFEQ algorithm achieved lower CRs, but also lower noise levels across all test signals.
Secondary user access for IoT applications in the FM radio band using FS-FBMC
Kenneth W. Barlee, Louise H. Crockett, Robert W. Stewart
IEEE First World Form on 5G, 2019
Abstract — In this paper a Dynamic Spectrum Access (DSA) Physical layer (PHY) technique is proposed that allows Secondary User (SU) access to the traditional FM Radio spectrum (88-108 MHz) for alternative data communication applications. FM radio waves have excellent propagation characteristics for long distance transmission, and have high levels of penetration through buildings. Using tools such as a structured geolocation database of licensed Primary User (PU) FM Radio transmitters, unlicensed SUs can access portions of the 20 MHz-wide band and transmit signals that place spectral ‘holes’ with suitable guard bands around all known PUs. Based on the PU protection ratios published by Ofcom and the FCC, the operation of a FBMC (Filter Bank Multi-Carrier) transmitter is demonstrated for an urban environment, and through ‘field test’ simulation it is shown that the Out Of Band (OOB) leakage of the proposed PHY (energy in the ‘holes’ that can interfere with the PU) is 47 dB lower than that of using an equivalent OFDM PHY. The results show that the proposed PHY is a suitable candidate for DSA-SU communication (e.g. in smart city IoT applications), whilst ensuring the integrity of incumbent PU signals.
A low-cost desktop software defined radio design environment using MATLAB, simulink, and the RTL-SDR
Robert W. Stewart, Louise H. Crockett, Dale Atkinson, Kenneth W. Barlee, David Crawford, Iain Chalmers, Mike McLernon, Ethem Sozer
IEEE Communications Magazine, 2015
Abstract — In the last 5 years, the availability of powerful DSP and Communications design software, and the emergence of relatively affordable devices that receive and digitize RF signals, has brought Software Defined Radio (SDR) to the desktops of many communications engineers. However, the more recent availability of very low cost SDR devices such as the RTL-SDR, costing less than $20, brings SDR to the home desktop of undergraduate and graduate students, as well as both professional engineers and the maker communities. Since the release of the various open source drivers for the RTL-SDR, many in the digital communications community have used this device to scan the RF spectrum and digitise I/Q signals that are being transmitted in the range 25MHz to 1.75GHz. This wide bandwidth enables the sampling of frequency bands containing signals such as FM radio, ISM signals, GSM, 3G and LTE mobile radio, GPS and so on. In this paper we will describe the opportunity and operation of the RTL-SDR, and the development of a hands-on, open-course for SDR. These educational materials can be integrated into core curriculum undergraduate and graduate courses, and will greatly enhance the teaching of DSP and communications theory, principles and applications. The lab and teaching materials have recently been used in Senior (4th year Undergraduate) courses and are available as open course materials for all to access, use and evolve.