Amit Kachroo | Oklahoma State University (original) (raw)

inproceedings by Amit Kachroo

This paper analyzes the physical relation between the power consumption and the link utilization ... more This paper analyzes the physical relation between the power consumption and the link utilization of wireless video sensor networks. It then proposes a method of multi-channel allocation and routing for multi-hop wireless sensor networks where each node is a battery-powered video camera sensor. Battery powered video camera sensors are often used in a form of a wireless mesh network to cover a large area. We analyze the power consumption model for a wireless link in terms of the distance and its utilization ratio. We present a formula of routing and channel allocation using only active sensor nodes in a way that minimizes the overall power consumption while ensuring transmission of the target video data. We developed a fast heuristic algorithm, and implemented it in a wireless video sensor network simulator. It introduces a notion of aggressor and victims of shared channels to calculate utilization incrementally as the routing algorithm proceeds. Extensive simulation results are provided with wireless video sensor networks of various sizes, which show the performance advantage of the proposed algorith

Papers by Amit Kachroo

2021 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS)

This paper introduces a method to de-embed motion artifacts introduced by cable movement during m... more This paper introduces a method to de-embed motion artifacts introduced by cable movement during millimeter wave propagation measurements that involve motion. In our work, the motion is performed by a Sawyer robotic arm emulating a UAV motion profile disturbed with gusts generated by the Dryden wind model. An RF cable connects the Rx from the end effector of the arm to a Keysight VNA taking time-swept continuous wave measurements. The cable moves with the arm, introducing phase changes to the measurement data. After determining the cable S-parameters in the continuous time domain, they are removed from the measurement data to get the channel parameters. Furthermore, the effects of de-emebedding is examined by comparing the Doppler spread of measurement data before and after de-embedding. The noise floor in the channel shifted from -62 dB before de-embedding to -58 dB after deembedding. The observed Doppler spread reduced by 31.67 Hz.

2018 26th Signal Processing and Communications Applications Conference (SIU), 2018

In this paper, an extended reduced-rank direction-of-arrival (DOA) estimation with unknown mutual... more In this paper, an extended reduced-rank direction-of-arrival (DOA) estimation with unknown mutual coupling in uniform linear array (ULA) structure is presented. The proposed method is based on the joint iterative subspace optimization (JIO) and the auto-calibration of mutual coupling. Given an initial coupling vector, reduced-rank correlation matrix is estimated with the JIO approach, followed by iterative joint estimation of DOA and coupling with an auto-calibration algorithm. Simulation results show that both the proposed method and the existing auto-calibration method have similar performance in terms of DOA root mean square error, while the complexity of the proposed method is much lower than that of the auto-calibration approach due to the reduced rank.

Lecture Notes in Electrical Engineering, 2018

Global Positioning Systems (GPS) are widely used in many navigational applications such as vehicl... more Global Positioning Systems (GPS) are widely used in many navigational applications such as vehicles, aircraft, and ships to find their speed and position. However, the main drawback of GPS is reliability, especially in an urban environment. Tall buildings reflect the signal and can make the receiver’s location appear 10 m or more from its actual position. This paper details a low-cost system designed to overcome this accuracy problem. The proposed system, termed as Position at Response (PaR), utilizes a laser and a network of transponders to locate the vehicle position more accurately than a GPS. The system can work for an indoor application as well. It is easily adaptable to new routes, paths, or destinations. Our preliminary test results show an accuracy within three percent, relative to the distance of the transponders.

Autonomous Airborne Wireless Networks, 2021

The characterization of ultra‐wideband (UWB) wireless channel is very important to design any UWB... more The characterization of ultra‐wideband (UWB) wireless channel is very important to design any UWB system for health‐related applications. This chapter focuses on the fundamental properties of the UWB channel and presents one of the first experimental off‐body studies between a human subject and an unmanned aerial vehicle (UAV) at 7.5 GHz of bandwidth. The study was conducted in two environments: indoors and outdoors, and the human subject in this work was patched at nine different body locations under line‐of‐sight (LoS) conditions, four different body locations under non‐line‐of‐sight (NLoS), and at two body locations for four different body postures (sitting, sleeping, standing, and bending). The idea is to determine the best patch antenna location from the captured measurement data. Akaike Information Criteria (AIC) was used for statistical testing to find the distribution that best characterizes the fading channels between different body locations and the UAV. It was found that ...

Ad Hoc Sens. Wirel. Networks, 2016

IEEE Transactions on Antennas and Propagation, 2021

In this paper, millimeter wave (mmWave) wireless channel characteristics for Unmanned Aerial Vehi... more In this paper, millimeter wave (mmWave) wireless channel characteristics for Unmanned Aerial Vehicles (UAVs) assisted communication is analyzed and studied by emulating the real UAV motion using a robotic arm. The UAV motion considers the turbulence caused by the wind gusts that is statistically modelled by the widely used Dryden wind model. The frequency under consideration is 28 GHz, and the environment is an indoor type. Various power thresholds are set to find the Doppler spread experienced by the UAV hovering motion under the Dryden wind turbulence. The highest Doppler spread was found to be-102.8 Hz and +91.33 Hz at the power threshold of-50 dB. Moreover, path loss exponent of 1.62 is found with the empirical data collected during the campaign. The deep-fading case during the measurements is also further studied with an another set of measurements that considers only lateral motion. The Rician fading model with a K-factor of 19.75 dB was found to best fit this channel fading model. This novel framework of emulating UAV motion will definitely help build and design future mmWave communication systems for UAVs in future.

Sensors, 2020

In this letter, we investigate the idea of interference spreading and its effect on bit error rat... more In this letter, we investigate the idea of interference spreading and its effect on bit error rate (BER) performance in a cognitive radio network (CRN). The interference spreading phenomenon is caused because of the random allocation of subcarriers in an orthogonal frequency division multiplexing (OFDM)-based CRN without any spectrum-sensing mechanism. The CRN assumed in this work is of underlay configuration, where the frequency bands are accessed concurrently by both primary users (PUs) and secondary users (SUs). With random allocation, subcarrier collisions occur among the carriers of primary users (PUs) and secondary users (SUs), leading to interference among subcarriers. This interference caused by subcarrier collisions spreads out across multiple subcarriers of PUs rather than on an individual PU, therefore avoiding high BER for an individual PU. Theoretical and simulated signal to interference and noise ratio (SINR) for collision and no-collision cases are validated for M-qua...

2018 IEEE 88th Vehicular Technology Conference (VTC-Fall), Aug 1, 2018

Most of the research in cognitive radio field is primarily focused on finding and improving secon... more Most of the research in cognitive radio field is primarily focused on finding and improving secondary user (SU) performance parameters such as bit error rate, outage probability and capacity etc. Less attention is being paid towards the other side of the network that is the primary network which is under interference from SU. Also, it is the primary user (PU) that decides upon the interference temperature constraint for power adaptation to maintain a certain level of quality of service while providing access to SUs. However, given the random nature of wireless communication, interference temperature can be regulated dynamically to overcome the bottlenecks in entire network performance. In order to do so, we need to analyze the primary network carefully. This study tries to fill this gap by analytically finding the closed form theoretical expressions for signal to interference and noise ratio (SINR), mean SINR, instantaneous capacity, mean capacity and outage probability of PU, while taking peak transmit power adaptation at SU into picture. Furthermore, the expressions generated are validated with the simulation results and it is found that our theoretical derivations are in perfect accord with the simulation outcomes.

IEEE Transactions on Vehicular Technology, 2020

In this paper, we present the case of utilizing interference temperature (IT) as a dynamic quanti... more In this paper, we present the case of utilizing interference temperature (IT) as a dynamic quantity rather than as a fixed quantity in an orthogonal frequency division multiple access (OFDMA) based spectrum sharing systems. The fundamental idea here is to reflect the changing capacity demand of primary user (PU) over time in setting the interference power threshold for secondary user (SU). This type of dynamic IT will allow the SU to opportunistically have higher transmit power during relaxed IT period, thereby resulting in higher network capacity. The cognitive radio network (CRN) considered in this paper has an underlay network configuration in which the available spectrum of the PU is accessed concurrently by SU provided that the interference power at the PU receiver from SU is under a certain power threshold. This power threshold is set to maintain and guarantee a certain level of quality of service (QoS) for PU network. Theoretical expressions for outage probability and mean capacity for SU network are derived, and validated with simulation results, and it is observed that utilizing dynamic IT results in high network performance gains as compared to utilizing a fixed IT in cognitive radio system.

Transactions on Emerging Telecommunications Technologies, 2019

2016 IEEE 37th Sarnoff Symposium, 2016

In this study, we describe the behavior of LTE over the sea and investigate the problem of radio ... more In this study, we describe the behavior of LTE over the sea and investigate the problem of radio resource block allocation in such SINR limited maritime channels. For simulations of such sea environment, we considered a network scenario of Bosphorus Strait in Istanbul, Turkey with different number of ships ferrying between two ports at a given time. After exploiting the network characteristics, we formulated and solved the radio resource allocation problem by max-min integer linear programming method. The radio resource allocation fairness in terms of Jain's fairness index was computed and it was compared with round robin and opportunistic methods. Results show that the max-min optimization method performs better than the opportunistic and round robin methods. This result in turn reflects that the max-min optimization method gives us the high minimum best throughput as compared to other two methods considering different ship density scenarios in the sea. Also, it was observed that as the number of ships begin to increase in the sea, the max-min method performs significantly better with good fairness as compared to the other two methods.

2015 International Wireless Communications and Mobile Computing Conference (IWCMC), 2015

The use of multiple channels often increases the capacity of a wireless network, especially, if t... more The use of multiple channels often increases the capacity of a wireless network, especially, if those channels are orthogonal. However, the challenge lies when we have more nodes than the available orthogonal channels. The 802.11n, 2.4 GHz WLAN has 3 orthogonal channels and 8 partially overlapping channels. These numbers of orthogonal channels put a limitation on the channel usage in a network and thus affect the overall network capacity. To overcome this degradation of network capacity with such limited channel scenario, we must focus on the transmission power of these nodes. In this paper, we describe a smart algorithm with realistic formulation, which divides the complex channel assignment and power optimization problem into two separate solution sets. First solution set solves the channel assignment problem in access points of the 802.11 infrastructure based network utilizing both orthogonal and overlapping channels and the second solution set improves the throughput of the network by optimizing the transmission power of these nodes. We selected optimal channel and transmission power assignment using the algorithm, and then ran simulations on a set of multi-AP WLAN. Experimental results show an improvement of approximately 14% in the throughput of infrastructure based 802.11n WLAN compared to previous work.

IEEE Access, 2019

In this paper, off-body ultra-wide band (UWB) channel characterization and modeling are presented... more In this paper, off-body ultra-wide band (UWB) channel characterization and modeling are presented between an unmanned aerial vehicle (UAV) and a human subject. The wearable antenna was patched at nine different body locations on a human subject during the experiment campaign. The prime objective of this work was to study and evaluate the distance and frequency dependent path loss factors for different bandwidths corresponding to various carrier frequencies, and also look into the time dispersion properties of such unmanned aerial vehicle-to-wearables (UAV2W) system. The environment under consideration was an indoor warehouse with highly conductive metallic walls and roof. Best fit statistical analysis using Akaike Information Criteria revealed that the Log-normal distribution is the best fit distribution to model the UWB fading statistics. The study in this paper will set up a road map for future UAV2W studies to develop enhanced retail and remote health-care monitoring/diagnostic systems. INDEX TERMS Ultra-wide band, unmanned aerial vehicle, off-body channel modeling, time dispersion parameters, path gain, path loss.