Department of Electrical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

&nbsp;

IIT Palakkad

With the emergence of cloud radio access network (C-RAN) architecture, latency in fronthaul (FH) network is a critical performance metric especially for ultra-reliable and low-latency communication applications. The stringent FH capacity and latency requirements of C-RAN can be relaxed by offloading some baseband functionalities to remote radio unit (RRU), referred to as functional splitting. This allows packetized FH network solutions such as ubiquitous Ethernet. In this paper, we calculate the FH latency in the uplink of a C-RAN system with massive MIMO-based RRUs and 3GPP functional Split 7, wherein MIMO equalization is done at the RRU. We derive tractable, closed-form expressions for the steady-state probabilities of queue length and sojourn time distribution at the output port of an Ethernet switch in the FH network. We first present these results for Poisson file arrivals from users in the network and exponential file size distribution. We then extend the results to general file size distribution. The numerical results show that the file size and spectral efficiency of the users are critical in determining the FH latency. Further, results show that switch speed can be decreased without incurring significant increase in FH latency revealing the possibility for statistical multiplexing gains. © 2019 IEEE.

World University root node

IEEE Wireless Communications and Networking Conference, WCNC

Latency in the Uplink of massive MIMO CRAN with Packetized Fronthaul: Modeling and Analysis

Cell-free massive multiple-input multiple-output (MIMO) is a promising cellular technology in which a large number of distributed access points (APs) jointly serve a small number of user equipments (UEs). In this work, we investigate the impact of the spatial distribution of APs on the performance of a cell-free massive MIMO system, considering different downlink power control policies. Further, we analyze the performance for the case where only subsets of all APs serve the individual UEs: this scenario has lower backhaul requirements and associated CAPEX/OPEX costs. In this framework, we first propose a novel, tractable approximation for the average spectral efficiency (SE) of the transmission to a UE conditioned on the estimated channel gains. This approximation is then used to develop different downlink power control policies. Further, we extend the policies to the scenario when power control is coordinated only among subsets of APs and not across the subsets. Through extensive system-level simulations, we evaluate the improvement in SE by spreading out the APs and the SE loss when a subset of all APs serve a UE and coordination across subsets is absent. © 2019 IEEE.

IEEE Vehicular Technology Conference

Downlink power control in cell-free massive MIMO with partially distributed access points

Cloud radio access network (C-RAN) and massive multiple-input-multiple-output (MIMO) are two key enabling technologies for 5G as they improve radio performance while lowering the cost of operation. In a C-RAN system with massive MIMO-based remote radio units (RRUs), fronthaul is often the bottleneck in practice due to its finite capacity. To reduce the capacity requirements on fronthaul, precoding is done at the RRUs. In this paper, we maximize the energy efficiency (EE) of such a system by optimizing the transmit powers while explicitly incorporating the capacity constraints on fronthaul. We develop a successive convex approximation (SCA) algorithm, which is guaranteed to converge to a local optimum. Towards this, we propose novel bounds on the user rate function, which facilitates a convex approximation of the EE maximization problem. The convex problem is solved in each SCA iteration through Dinkel-bach's algorithm and dual decomposition. Numerical results show that the proposed algorithm significantly improves EE compared to the case with no power control and outperforms the weighted minimum mean square error algorithm. © 2019 IEEE.

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC

Energy Efficiency Maximization in Massive MIMO-aided, Fronthaul-constrained C-RAN

The present numerical analysis aims at studying the effect of changes in profile of van on aero-acoustic noise and aerodynamic drag. The numerical analysis is carried out using commercial CFD software, ANSYS Fluent, with k-epsilon & Large Eddy Simulation turbulence models. In present study five models of truck are analysed, including baseline model at different Reynolds numbers, namely 0.391, 0.415 and 0.457 million. In order to reduce the aero-acoustic noise, various profile modifications have been adapted on existing van model by adding a top and bottom diffuser at the rear of the truck. The comparison has been done with respect to coefficient of drag, coefficient of pressure, pressure contours for all four cases. It is observed from the simulation results among different modifications of truck, adding a top and bottom diffuser of 15 degrees at the rear end of truck gives the maximum reduction in aero-acoustic noise up to 9.4% and aerodynamic drag reduction of 3.8 % as compared to baseline model, at a speed of 81 km/h. © 2019 SAE International. All Rights Reserved.

SAE Technical Papers

Attenuation of Aeroacoustic Noise of a Typical Van Using Passive Devices through CFD Simulation

The control of a spacecraft equipped with a six-degree-of-freedom robot manipulator is studied in this paper. The objective is to rendezvous and synchronize with a satellite to facilitate inspection, servicing or de-orbiting. The space manipulator dynamics model with global parameterization on the configuration manifold is derived and used for designing asymptotically-stable control laws, so that they are valid globally in the configuration manifold. The control system consists of a sliding-mode rendezvous controller as well as a geometric attitude synchronization and a model-based servo control for the robot manipulator. The gains of the sliding-mode controller dictate a user-defined upper-bound on the thrust force. The attitude synchronization controller, concurrently with the rendezvous controller, is capable of micro-orbiting the space manipulator around spinning or tumbling satellites. It is observed through the simulations that the controller consumes limited amount of propellant, and it is feasible to use it for either a re-fueling (larger mass) or a de-orbiting (smaller mass) space manipulator. © 2019, American Astronautical Society.

Journal of the Astronautical Sciences

Rendezvous and Attitude Synchronization of a Space Manipulator

The design, development, and characterization of broadband (1–30 GHz) micro electromechanical systems (MEMS) based electrostatically driven lateral switching networks are presented in this paper. Initially, single switch performances are optimized, and later it is used to develop different switching networks like single-pole-double-throw (SPDT), single-pole-three-throw (SP3T), and single-pole-six-throw (SP6T). All switches are extensively characterized including reliability testing. Switching networks demonstrate measured return loss of better than 21 dB (11.4 dB) with worst case insertion loss of 0.67 dB (∼5 dB) and isolation of better than 31 dB (17.7 dB) at 3.5 GHz (28 GHz) for 5G communications. Switching networks tested for &gt; 1 billion cycles with 1 W of RF power are found to be operational. Maximum fabricated switch (SP6T) area is ∼0.7 mm2 including bias lines and pads. © 2019, Electromagnetics Academy. All rights reserved.

Progress In Electromagnetics Research M

Compact, broadband and reliable lateral MEMS switching networks for 5G communications

Microgrid mandates a highly accurate and reliable protection measure for safe and secure operation. Reliability of the protecting system becomes a serious concern when the microgrid operates with various types of DG units which includes synchronous, induction and inverter based DGs with different topology and modes of operation. This paper demonstrates an intelligent protection scheme using deep neural network (DNN) to perform the task of fault detection and classification. Fault currents retrieved at the relaying points are given to the proposed protection scheme to perform the desired task. The performance of the scheme is measured with wide variations in system parameters such as modes of operation and network topologies of the microgrid. The scheme is extensively tested on a large dataset even by varying types of inputs and different deep neural network structures. The test results and response time show that the proposed algorithm can be used in real time for protective measures of microgrid. © 2019 IEEE.

2019 8th International Conference on Power Systems: Transition towards Sustainable, Smart and Flexible Grids, ICPS 2019

A DNN based Intelligent Protective Relaying Scheme for Microgrids

Water vapor is of one of the most important constituents of Venus atmosphere because of its involvement in the formation of cloud, thermal balance and atmospheric chemistry. Water vapour abundance is approximately 30 ppm from ground up to an altitude of approximately 40 km, which is also the limit for Venus clouds. Infrared radiometer (PVOIR) measurements [1, 2, 3] from the 1978–1979 Pioneer Venus Orbiter show that cloud top water vapor has a strong diurnal variation. This variation could be ± 5 ppmv at night for 10 ppmv water vapour content, and daytime values could vary at ± 15 ppmv for values of 90 ppmv. In contrast, 15 Fourier Transform spectrometer (FTS) data from 1983 Venera [3, 4] show that cloud top water vapour abundances is of 7-17 ppmv, with no diurnal variability. Similarly, Earth-based infrared spectroscopy [5] measurements indicate that water vapour mixing ratios is in the range of 0.5 to 40 ppm in the altitude range 62–65 km. Despite the multiple measurements sources, accurate information about water vapour variations is still not available. This variation in the available information may be due to difference in the sounded altitude range, experimental and modeling errors. © 2019 URSI. All rights reserved.

2019 URSI Asia-Pacific Radio Science Conference, AP-RASC 2019

Design of millimeter-wave radiometer for measuring water vapour in venus atmosphere

A novel predictive current controller is proposed for a three-phase two-level active front end rectifier using virtual vector switching. Lyapunov stability criteria is applied to optimise the angle and magnitude of the virtual converter voltage vector to be applied at each sampling instant. The optimal virtual vector is then realised using suitable space vector modulation technique, thereby ensuring a constant switching frequency of operation of the converter. Since active front end converters are desired to operate at unity power factor, 60° continual bus clamping space vector modulation is employed to reduce the switching losses. The proposed controller thus ensures optimum operation of the converter at a fixed switching frequency, similar to conventional model predictive controllers along with the reduction in line current ripple, improved line current quality, minimal switching losses and less computational burden on the controller. The efficacy of the proposed controller is investigated for a two level active front end rectifier and the simulation results are presented. © 2019 IEEE.

IECON Proceedings (Industrial Electronics Conference)

A Novel Predictive Control for an Active Front End Rectifier using Lyapunov Stability Criteria

Unstable power swing (UPS) may cause unwanted zone-1 tripping. This is caused due to presence of electrical center within the reach of zone-1 of distance relay. Fast detection of unstable swing can assist distance relay in taking reliable decision. This paper suggests a new coordinate system with transient potential power as the y-coordinate and angular difference of positive sequence voltage phasors across the transmission line ({{\boldsymbol{\delta }}-{{\boldsymbol{\text{SR}}}}}) as the x-coordinate. We observed that this coordinate system can be useful to successfully differentiate an UPS from stable power swing (SPS) and three phase fault. The prediction is fast enough to prevent an unwanted zone-1 operation of distance relay. IEEE-39 bus New England test system is used to validate the proposed scheme. The suggested method showed improved and fast unstable swing detection accuracy under different pre-disturbance and fault conditions. © 2007-2012 IEEE.