Ardavan Rahimian

Microwave beamforming networks employing Rotman lenses and cascaded Butler matrices for automotive communications beam scanning electronically steered arrays

This paper presents the novel designs of steerable microwave beamforming networks (BFNs) employing a 4×4 Rotman Lens for operation at 3.15 GHz (S-band), an 8×8 Rotman Lens for operation at 6.3 GHz (C-band), and cascaded 4×4 Buter Matrcies for operation at 3.15 GHz (S-band). The microwave beamforming networks are intended for automotive communications beam scanning electronically steered arrays. Although the frequency range likely to be allocated to such systems is 63 GHz, where the short transmission range allows multiple frequency re-use, the planar beamforming networks are frequency scaled models to verify the concept. The objective of this investigation is to develop microwave beamforming networks suitable for a use in inter-vehicle (IVC) and roadside-to-vehicle (RVC) automotive communications electronically steered arrays. The steerable microwave beamforming networks demonstrate appropriateness to develop well-established designs for systems that can be used in automotive communications beam scanning electronically steered array and vehicular telematics.

Enhanced RF steerable beamforming networks based on butler matrix and rotman lens for ITS applications

This paper presents the design, simulation, and fabrication of two RF steerable beamforming networks (BFN) using a 4×4 Butler Matrix for the 3.15 GHz (S-band) and an 8×8 Rotman Lens for the 6.3 GHz (C-band). Both beamforming networks are intended for the Intelligent Transportation Systems (ITS). Although the frequency range likely to be allocated to such systems is 63 GHz, where the short transmission range allows multiple frequency reuse, both networks are frequency scaled models to verify the concept. The objective of this investigation is to develop steerable antennas suitable for a use in vehicle-to-vehicle and vehicle-to-roadside communications systems. The antenna array feeding network based on Butler Matrix is optimized using a Genetic Algorithm (GA). A GA is used to determine the optimum dimensions for the hybrid couplers and crossovers as the key elements of the network. The Butler Matrix produces orthogonal beams that can be steered in different directions. The lens-based beamformer based on Rotman Lens is capable of generating multiple beams for Electronic Scanning Arrays (ESA) and wide-band operation. To examine the performance of the proposed networks, simulated and measured results are presented and discussed. The results also demonstrate GAs appropriateness to hybrid couplers and network optimization and enhancement to develop well-established designs for systems that can be used in vehicular telematics and ITS applications.

Analytical and numerical evaluations of flexible V-band rotman lens beamforming network performance for conformal wireless subsystems

This paper presents the analytical design and numerical performance evaluation of novel V-band millimetre-wave (mm-wave) beamforming networks (BFNs), based on the Rotman lens array feeding concept. The devices are intended for operation in the unlicensed 60-GHz frequency band. The primary objective of this work is to study the feasibility of designing flexible V-band beamformers, based on liquid-crystal polymer (LCP) substrates. The planar Rotman lens device has been initially developed, and the output performances, in terms of the scattering parameters and accuracy, have been analysed. This is further continued with the detailed designs of the Rotman lens BFNs based on the four different proposed flexural cases, namely the concave-axial bending, the convex-axial bending, the concave-circumferential bending, and the convex-circumferential bending. Each of the flexures has been analysed, and the performance in terms of the surface currents and phase distributions, as the primary functionality indicators, has been presented. The presented flexible beamformers exhibit significant characteristics to be potentially employed as low-cost and efficient units of the mm-wave transceivers with the in-built electronic beam steering capabilities for the conformal wireless subsystems.

Investigation of Nolen matrix beamformer usability for capacity analysis in wireless MIMO systems

This short paper presents the investigation of Nolen matrix beamforming network usability for capacity enhancement in wireless multiple-input multiple-output (MIMO) systems. The objective of this research is to thoroughly analyze and develop an analytical and mathematically-oriented investigation into system MIMO capacity improvement using a circuit-based beamformer. The evaluation RF modeling demonstrates the appropriateness to develop a well-established microwave analysis for the wireless RF systems based on the circuit-microwave beamforming networks.

Short-length FSU-SCQICs over coherent and incoherent stochastic aeronautical MISO channels

Multi-antenna systems play a major role in modern wireless systems due to their outstanding capability in alleviating deconstructive addition of multipath echoes and interferences from other users in wireless media. However, the performance of numerous technologies such as high-performance forward error correction (FEC) codes still have not been sufficiently examined under various multi-antenna wireless propagation environments. This short paper presents the performance of the integrated fully systematic unpunctured (FSU) serial concatenation of quadratic interleaved codes (SCQICs) and Alamouti dual-antenna space-time codes over coherent and incoherent stochastic aeronautical multiple-input single-output (MISO) wireless propagation links.

A flexible printed millimetre-wave beamforming network for WiGig and 5G wireless subsystems

This paper presents a novel millimetre-wave (mm-wave) array beamforming network (BFN) design, analysis, and implementation based on the Rotman lens antenna array feeding, intended for operation in the unlicensed 60-GHz frequency band for the potential employment in the fifth-generation (5G) cellular communications and WiGig technology. The primary objective of the work is to thoroughly discuss the advanced cellular network, and to further develop a flexible radio frequency (RF) component based on the polyethylene terephthalate (PET) substrate using the in-house inkjet materials printing process, for the mm-wave beam steering concept verification. The RF evaluation modeling demonstrates the appropriateness to develop a high-performance and well-established design for the WiGig and 5G systems, along with the analysis of the RF characteristics. The CST Microwave Studio and MATLAB software are employed in order to conduct the modelling and full-wave electromagnetic (EM) simulations.

Serial concatenation of quadratic interleaved codes in different wireless doppler environments

The remarkable development of mobile networks has enabled ubiquitous communications that has transformed the way people connect with each other. Meanwhile, the growing adoption of smartphones, tablets, and increasingly bandwidth-intensive applications and services is driving unprecedented mobile broadband traffic growth; therefore, finding state-of-the-art strategies for improving the wireless transmission reliability has emerged significantly. In particular, to enable significant mitigation of the detrimental effects of multipath fading, high-performance forward error correction (FEC) techniques have now recognized to become a vital part of modern digital wireless systems. This work is dedicated to address a class of high-performance iteratively decoded FECs referred to as serial concatenation of quadratic interleaved codes (SCQICs) wherein the reordering arrays for permutor and unscramble in the FEC encoding/decoding entities enjoy the remarkable algorithm proposed by Takeshita et al. seminal contribution which: (1) yields provisioning coding gain in both waterfall and error-floor regions of the bit error rate (BER) performance curve (2) enables possibility of analysis and compact representation, (3) requires straightforward implementation. We have observed that their utilization for the modern wireless communications applications remained scarce due to the lack of strong and comprehensive performance predictions over the different statistical wireless channel models. Hence, in this paper, we endeavor to analyze and examine the error-correction capability of SCQICs vastly from the various aspects, and investigate their resultant coding gains in different wireless Doppler environments.

Joint space-time algebraically-interleaved turbo-like Coded Incoherent MIMO systems with optimal and suboptimal MAP probability decoders

The outstanding coding gains and also the practical complexities of the turbo-coded communication systems, heavily depend on the iterative soft-decision decoding algorithm used for the soft-input/-output component decoders. The goal of this paper is to address the investigation on the energy gaps of the enhanced channel coding entity of [1], when original and also approximated logarithmic-based iterative MAP algorithms are employed for the iterative near maximum-likelihood (ML) decoding. As far as the large decoding delays of the turbo and turbo-like code structures constitute a major disadvantage for these types of channel-codes, the previously introduced high-performance channel-codes of [1] are developed for the original and also approximated iterative BCJR-MAP turbo decoders to enable the higher level of selection flexibility in error-rate versus computational complexity tradeoff. We examine the required energy per bit Eb and the noise power spectral density N0 ratio to attain the BER ≈ 10-4 - 10-5 for the differentially encoded phase-shift keying (D-PSK) MIMO Rayleigh fading channels.

Energy Management Using a Situational Awareness-Centric Ad-Hoc Network in a Home Environment

Energy management theory and techniques for home environments are facing several technical challenges in areas including the real-time scheduling, power distribution, and automation of network of home appliances/renewables for achieving maximum energy efficiency. In this paper, situational awareness (SA) has made this crucial decision making process more efficient, by providing the valuable data about the surrounding environment. In a smart home, apart from the electrical appliances, the intelligent sensors are also consuming energy while transmitting data or when they are in idle mode. In this contribution, our focus is on implementing and analysing a situational awareness-based ad-hoc network in a home environment, in order to reduce the energy consumption, and therefore, increasing the lifetime of these networks. The presented results demonstrate the effectiveness of the proposed SA-centric method, and further confirm the energy consumption in the intended environment is decreased dramatically due to the applied schedule and limitations on the working hours of the devices. Moreover, the sensors are switched to doze mode when there is no data to exchange.

DESIGN AND PERFORMANCE ANALYSIS OF MILLIMETRE-WAVE ROTMAN LENS-BASED ARRAY BEAMFORMING NETWORKS FOR LARGE-SCALE ANTENNA SUBSYSTEMS

This paper presents the comprehensive analytical design and numerical performance evaluation of novel millimetre-wave (mm-wave) switched-beam networks, based on the Rotman lens (RL) array feeding concept. These passive array devices have been designed for operation in the 28GHz frequency band, covering the whole 18–38 GHz frequency range. The primary objective of the work is to conduct a thorough feasibility study of designing wideband mm-wave beamformers based on liquid-crystal polymer (LCP) substrates, to be potentially employed as low-cost and high-performance subsystems for the advanced transceiver units and large-scale antennas. The presented RLs exhibit significant output behaviours for electronic beam steering, in terms of the scattering (S) parameters, phase characteristics, and surface current distributions, as the feeding systems’ primary functionality indicators.