Beamforming in MISO Systems: Empirical Results and EVM-based Analysis

We present an analytical, simulation, and experimental-based study of beamforming Multiple Input Single Output (MISO) systems. We analyze the performance of beamforming MISO systems taking into account implementation complexity and effects of imperfect channel estimate, delayed feedback, real Radio Frequency (RF) hardware, and imperfect timing synchronization. Our results show that efficient implementation of codebook-based beamforming MISO systems with good performance is feasible in the presence of channel and implementation-induced imperfections. As part of our study we develop a framework for Average Error Vector Magnitude Squared (AEVMS)-based analysis of beamforming MISO systems which facilitates comparison of analytical, simulation, and experimental results on the same scale. In addition, AEVMS allows fair comparison of experimental results obtained from different wireless testbeds. We derive novel expressions for the AEVMS of beamforming MISO systems and show how the AEVMS relates to important system characteristics like the diversity gain, coding gain, and error floor.Comment: Submitted to IEEE Transactions on Wireless Communications, November 200

Systems and environmental decision-making: postgraduate open learning with the Open University

Environmental issues affect everyone though the ways in which people engage with them varies a great deal. The Open University''s Masters program in environmental decision making has at its core a modular course that enables students to incorporate environmental factors into their decision making from a starting point of identifying their own environmental issues using a systems approach. Students carry out a project based on their own experience in a decision-making situation of their own choice. A framework for environmental decision making is introduced and students learn how to use the framework systematically, systemically and critically. The course has evolved since it was first introduced in 1997 as both students and the course team have learnt about environmental decision making together. This paper analyses and interprets some of the data that have emerged from students projects since the course began

Large-Scale MIMO Detection for 3GPP LTE: Algorithms and FPGA Implementations

Large-scale (or massive) multiple-input multiple-output (MIMO) is expected to be one of the key technologies in next-generation multi-user cellular systems, based on the upcoming 3GPP LTE Release 12 standard, for example. In this work, we propose - to the best of our knowledge - the first VLSI design enabling high-throughput data detection in single-carrier frequency-division multiple access (SC-FDMA)-based large-scale MIMO systems. We propose a new approximate matrix inversion algorithm relying on a Neumann series expansion, which substantially reduces the complexity of linear data detection. We analyze the associated error, and we compare its performance and complexity to those of an exact linear detector. We present corresponding VLSI architectures, which perform exact and approximate soft-output detection for large-scale MIMO systems with various antenna/user configurations. Reference implementation results for a Xilinx Virtex-7 XC7VX980T FPGA show that our designs are able to achieve more than 600 Mb/s for a 128 antenna, 8 user 3GPP LTE-based large-scale MIMO system. We finally provide a performance/complexity trade-off comparison using the presented FPGA designs, which reveals that the detector circuit of choice is determined by the ratio between BS antennas and users, as well as the desired error-rate performance.Comment: To appear in the IEEE Journal of Selected Topics in Signal Processin

Temporal trends in spider communities at the UK Environmental Change Network Cairngorm field station, 2007-2019: data analysis report

This report details the trends in spider abundance at the Environmental Change Network (ECN) Cairngorms site over 13 years (2007-2019). Spiders were collected from pitfall traps in three habitats (pine woodland, wind-clipped heath, bog) in the Allt a’Mharcaidh catchment near Feshiebridge in the Western regions of the Cairngorms National Park, Scotland. Data was collected using standard ECN protocol, and all collected spider specimens were identified by the same expert araneologist for consistency. The spider communities were diverse, but typical of upland sites in the region, whilst a number of species present were either nationally rare, scarce, or amber listed due to nationwide declines. Over the relatively short period of monitoring none of the 96 species recorded at the site were found to be declining in abundance, whilst 16 species increased. The woodland community had the highest richness of species, consistent with this habitat being the most ecologically accessible to generalist species. Overall, however, abundances were similar across spider communities occupying the woodland, bog and heath habitats. The woodland community also appears to be becoming increasingly stable over time, relative to the heath and bog communities, both of which appeared to show extensive community change in 2013, which lasted for five years. This is likely a response to environmental extremes that occurred during the autumn of 2012 and spring / summer of 2013, but further exploratory research is required

Experiment-driven Characterization of Full-Duplex Wireless Systems

We present an experiment-based characterization of passive suppression and active self-interference cancellation mechanisms in full-duplex wireless communication systems. In particular, we consider passive suppression due to antenna separation at the same node, and active cancellation in analog and/or digital domain. First, we show that the average amount of cancellation increases for active cancellation techniques as the received self-interference power increases. Our characterization of the average cancellation as a function of the self-interference power allows us to show that for a constant signal-to-interference ratio at the receiver antenna (before any active cancellation is applied), the rate of a full-duplex link increases as the self-interference power increases. Second, we show that applying digital cancellation after analog cancellation can sometimes increase the self-interference, and thus digital cancellation is more effective when applied selectively based on measured suppression values. Third, we complete our study of the impact of self-interference cancellation mechanisms by characterizing the probability distribution of the self-interference channel before and after cancellation.Comment: Revised the submission to IEEE Transactions on Wireless Communications, May 2012. Submitted to IEEE Transactions on Wireless Communications, July 201

Improving MIMO Sphere Detection Through Antenna Detection Order Scheduling

This paper proposes a novel scalable Multiple-Input Multiple-Output (MIMO) detector that does not require preprocessing to achieve good bit error rate (BER) performance. MIMO processing is a key technology in broadband wireless technologies such as 3G LTE, WiMAX, and 802.11n. Existing detectors such as Flexsphere use preprocessing before MIMO detection to improve performance. Instead of costly preprocessing, the proposed detector schedules multiple search passes, where each search pass detects the transmit stream with a different permuted detection order. By changing the number of parallel search passes, we show that this scalable detector can achieve comparable performance to Flexsphere with reduced resource requirement, or can eliminate LLR clipping and achieve BER performance within 0.25 dB of exhaustive search with increased resource requirement

Low Complexity Hybrid Beamforming for mmWave Full-Duplex Integrated Access and Backhaul

We consider an integrated access and backhaul (IAB) node operating in full-duplex (FD) mode. We analyze simultaneous transmission from the New Radio gNB to the IAB node on the backhaul uplink, IAB node to a user equipment (UE) on the access downlink, and IAB transmitter to the IAB receiver on the self-interference (SI) channel. Our contributions include (1) a low complexity algorithm to jointly design the hybrid analog/digital beamformers for all three nodes to maximize the sum spectral efficiency of the access and backhaul links by canceling SI and maximizing received power; (2) derivation of all-digital beamforming and spectral efficiency upper bound for use in benchmarking; and (3) simulations to compare full vs. half duplex modes, hybrid vs. all-digital beamforming algorithms, proposed hybrid vs. conventional beamforming algorithms, and spectral efficiency upper bound. In simulations, the proposed algorithm shows significant reduction in SI power and increase in sum spectral efficiency