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Iain B. Collings - IEEE Xplore Author Profile

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This paper considers multiuser millimeter wave (mmWave) MIMO communication systems where both the base station (BS) and the user equipments (UEs) use analog beamforming (BF). We propose a beam acquisition approach to find the best directions for the narrow beams, required to achieve BS-UE links above a minimum signal-to-noise ratio (SNR) threshold. The multiple UEs first select their beams simulta...Show More
Millimeter wave (mm-Wave) frequencies provide high data rates while encountering issues like high penetration losses and obstruction. To overcome these challenges, large antenna arrays and analog beamforming with phase shifters are utilized. This can lead to overlapping coverage areas and interference between beams, making resource scheduling (user, beam, time, and data rate) a complex and critica...Show More
This paper presents an efficient approach for finding the optimal 3D deployment locations of multiple UAV base stations, to maximize the probability of connection for users uniformly distributed over a wide area. We consider covering a two-dimensional built urban environment with UAVs arranged in a regular equilateral triangle structure. We propose to provide a degree of overlapping coverage betwe...Show More
Low Earth Orbit (LEO) satellites are increasingly being used to provide connectivity for wide area Internet of Things (IoT) sensing applications. Distributed IoT terminals are not able to coordinate their uplink transmissions to the nano-satellites, and so operate in a grant-free mode. Quality-of-Service (QoS) depends on the transmission attempt success statistics, which are time-varying. This pap...Show More
The research presents a data dense passive chipless RFID Tag for multi-parameter sensing applications as a low-cost solution. The proposed circular tag is designed via approach of dual sided slot embedding. The tag yields 20-bit RCS response while staying in 20mm x 20mm dimensions. The data capacity has been amazingly enhanced compared to previous work. Taconic CER-10-0500 has been used as substra...Show More
This paper considers millimeter-wave (mmWave) networks with hybrid beamforming communications, where base stations have a limited number of radio frequency (RF) chains. The base stations have overlapping coverage to overcome blockage issues in both downlink and uplink transmission. We propose a user association (UA) scheme that minimizes the time required for clearing data traffic of users in the ...Show More
This paper analyses the data message success rate for Internet of Things (IoT) sensing devices communicating over Low Earth Orbit (LEO) satellite links. We present an analytical framework for optimizing multi-objective multi-packet reception on the uplink. We present an analytical result for the probability of message success for a given ground terminal, and present an analytical result for the ov...Show More
This article presents a new connectivity model for UAV-to-ground communication, when the UAV has a dipole antenna. Our model includes the impact of antenna length and impedance, on the radiation pattern. We present a new multi-ring two-tier connectivity model and show that the ground coverage area from the UAV consists of multiple circular annuli. We use the model to find the expected number of co...Show More
This paper presents optimal receiver implementations for Zak-OTFS modulation. Zak-OTFS has a receiver structure that includes a twisted convolution filter followed by delay-Doppler domain sampling. We first show that this receiver is equivalent to a correlation demodulator where the receive pulses are determined by the choice of the receive delay-Doppler domain twisted convolution (TC) filter. We ...Show More
This paper provides capacity results for multi-user mm-wave hybrid-beamforming, and presents optimal joint beam allocation and user scheduling algorithms. We characterize the downlink capacity of a practical system with quantized analog beamforming code-books under the constraint that users cannot be scheduled at the same time if they are closer together than a beam width in angle. We show that th...Show More
This research presents a low-cost solution towards passive identification and sensing of temperature for multi-applications being vital enablers to sense/measure remote parameters in pervasive artificial intelligent networks. The paper provides a glimpse of temperature sensitive tags with varying parameters/dimensions, number of bits and layout. Two different techniques are encountered for tempera...Show More
This paper presents a new OFDM based modulation scheme for communication in doubly dispersive channels. We call this Delay-Doppler OFDM (DD-OFDM). Our waveform has the same sparse-channel benefits as orthogonal-time-frequency-space (OTFS) modulation, while offering advantages in terms of simpler channel estimation, lower symbol error rate and lower out-of-band (OOB) emissions. We propose the DD-OF...Show More
This paper presents an efficient practical Zak-OTFS modulation implementation using time and frequency windowing methods. We present two general classes of delay-Doppler (DD) twisted convolution (TC) filters (Type-1 and Type-2), and show that they can be realized by time and frequency windowing functions. We then propose practical methods to generate time domain Zak-OTFS signals, for actual transm...Show More
This paper designs energy-efficient trajectories for unmanned aerial vehicles (UAVs) harvesting data sequentially from distributed ground nodes. We propose a novel optimization framework for path planning, based on dynamic programming. We develop an optimum backward-forward algorithm that jointly optimizes the hovering locations for each ground node, and the visiting order to those locations. Our ...Show More
Inappropriate material management in recycling chains lead to adverse effects of metals and glass inoculation in the plastic-only recyclable units/chains. Despite multiple ways to sort out plastic materials in garbage bins and large scale recycle units, intensive efforts are still needed to map the high cost and optic/light sensors drawbacks. In this paper, we propose a low-cost passive solution t...Show More
In this paper, we consider a millimeter wave network deployed to cover an urban street. Each base station (BS) employs hybrid beamforming with a limited number of radio frequency (RF) chains. Its link to any user equipment (UE) is prone to being blocked by vehicles and pedestrians moving along the street. We propose a Round Robin (RR) access protocol with proactive cell switching in which each UE ...Show More
This paper proposes an efficient 3D deployment approach for multiple UAV base stations, to maximize the probability of connections for users spread over a wide area. We consider covering a circular region, such as might apply in a disaster scenario affecting a city centre where terrestrial base stations have become inoperable. We compare two approaches to deploying UAVs. One is a regular triangula...Show More
This research article is intended to provide a solution for high-cost wireless identification and sensing applications. The paper yields application specific wireless, design-oriented battery-free transponder. A 2-bit clipless RFID (radio frequency identification) tag has been originated to map with ISM (industrial, scientific, and medical) radio band applications. The transponder resonates at 2.4...Show More
This article presents a 25-bit dual sided, passive chipless RFID tag. The novelty of research relies on the concept of utilizing ground area of tag to incorporate alternating metals and slits in reference to the structure on top of the substrate, hence yielding high code density. Compared to previous latest research, the structure and data capacity are significantly improved. The tag has been desi...Show More
This paper presents a new approach to estimate the probability of line-of-sight (LoS) for unmanned aerial vehicle (UAV) communications. We provide lower and upper bounds on the probability of LoS in terms of what we call the first-building-LoS probability. We provide a statistical model for the ground distance to the first building along the line from the user to the UAV. Based on this we provide ...Show More
This paper considers the implementation of compressive sensing (CS) approaches for beam alignment (BA) in multiuser millimeter wave (mmWave) MIMO systems. We particularly consider wideband time-varying channels in the practical low SNR regime. We examine two different time scales for beam-switching in the BA training phase at both the base station (BS) and the user equipment (UE). We also compare ...Show More
We consider compressive sensing (CS)-based beam alignment for time-varying millimeter wave (mmWave) MIMO channels. We propose a symbol-based beam switching (SBBS) approach with channel-probing beams being switched every OFDM symbol. We use the SBBS to measure second order statistics of the channel, which are used for sparse recovery. We formulate the problem for a wideband channel model with pulse...Show More
This paper considers the problem of determining the optimal flying locations for multiple UAV base stations to maximize the number of connected users. We consider the case of non-uniformly distributed users. We propose an adhoc approach to find optimal 3D UAV placement using a gravity inspired clustering algorithm and a two-tier connectivity model. We compare our proposed approach with existing ap...Show More
This paper considers millimeter wave (mmWave) MIMO communication systems that employ analog beamforming. We propose a new two-phase beam acquisition algorithm for the practical multiuser scenario. The algorithm is based on efficiently searching beamforming codebooks at the base station (BS) and the mobile devices (user equipment, UE). In the downlink training phase, the BS broadcasts a training si...Show More
This paper presents an accurate approach to predict the probability of line-of-sight for unmanned aerial vehicle (UAV) communications. We present a new numerical approach to calculate the probability of line-of-sight as a function of UAV height and distance to a ground based receiver, using a two- dimensional model of building and UAV locations. We use this numerical approach to calculate the prob...Show More