Mehul Motani

Mehul Motani
National University of Singapore | NUS · Department of Electrical & Computer Engineering

PhD

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285
Publications
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Introduction
Skills and Expertise

Publications

Publications (285)
Preprint
Accurate long-range forecasting of time series data is an important problem in many sectors, such as energy, healthcare, and finance. In recent years, Generative Adversarial Networks (GAN) have provided a revolutionary approach to many problems. However, the use of GAN to improve long-range time series forecasting remains relatively unexplored. In...
Preprint
We explore a new perspective on adapting the learning rate (LR) schedule to improve the performance of the ReLU-based network as it is iteratively pruned. Our work and contribution consist of four parts: (i) We find that, as the ReLU-based network is iteratively pruned, the distribution of weight gradients tends to become narrower. This leads to th...
Article
Full-text available
Energy harvesting (EH) relay communication systems with decoding energy costs in multiple block cases have not been widely studied. This paper investigates the relay network with a decode-and-forward relay powered by EH. Unlike other works, we consider the relay with energy decoding costs which harvests random energy from both a dedicated transmitt...
Article
Freshness of information is an important requirement in many real-time applications. It is measured by a metric called the age of information (AoI), defined as the time elapsed since the generation of the last successful update received by the destination. We consider $M$ sources (users) updating their statuses to a base station (BS) over a block...
Article
Constrained coding is used widely in digital communication and storage systems. In this article, we study a generalized sliding window constraint called the skip-sliding window. A skip-sliding window (SSW) code is defined in terms of the length $L$ of a sliding window, skip length $J$ , and cost constraint $E$ in each sliding window. Each val...
Chapter
State-of-the art machine learning (ML) methods show immense promise for medical applications, offering significant improvement in prediction capabilities for electronic health record (EHR) data. However, the models’ black-box nature make it difficult for an end-user to trace the decision-making process, a key challenge for the application of machin...
Article
In emerging fifth generation and beyond wireless communication systems, communication nodes are expected to support information flows that are freshness-sensitive , along with broadband traffic having high data rate requirements. Freshness-sensitive flows, where freshness is quantified by a metric called the age of information (AoI), are natura...
Article
We apply the generalized sphere-packing bound to two classes of subblock-constrained codes. À la Fazeli et al. (2015), we make use of automorphisms to significantly reduce the number of variables in the associated linear programming problem. In particular, we study binary constant subblock-composition codes (CSCCs), characterized by the prope...
Chapter
Full-text available
Energy harvesting (EH) is of prime importance for enabling the Internet of Things (IoT) networks. Although, energy harvesting relays have been considered in the literature, most of the studies do not account for the processing costs, such as the decoding cost in a decode-and-forward (DF) relay. However, it is known that the decoding cost amounts to...
Chapter
Energy harvesting (EH) from natural and man-made sources is of prime importance for enabling the Internet of Things (IoT) networks. Although, energy harvesting relays in a relay network, which form building blocks of an IoT network, have been considered in the literature, most of the studies do not account for the processing costs, such as the deco...
Article
We propose the use of binary skip-sliding window (SSW) codes in the emerging area of simultaneous energy and information transfer, where the receiver uses the received signal for decoding information as well as for harvesting energy to run its circuitry. Binary SSW codes satisfy certain weight constraints over a skip-sliding window, and generalize...
Article
Crowdsourcing is an emerging paradigm for human-powered problem solving in the Internet of Things (IoT) era. In this paper, we consider the online task allocation problem in crowdsourcing systems. Instead of considering real-time tasks that need to be completed immediately, we allow delay tolerant tasks which workers can complete at their own pace...
Article
Full-text available
Lens antenna arrays have become attractive for mmWave MIMO systems due to their energy-focusing and path-division properties. However, when the signals cannot be well differentiated at different array elements due to their similar incident angles, we cannot estimate their DoAs separately. In this paper, we present a DoA estimation algorithm for thi...
Preprint
In the emerging fifth generation (5G) technology, communication nodes are expected to support two crucial classes of information traffic, namely, the enhanced mobile broadband (eMBB) traffic with high data rate requirements, and ultra-reliable low-latency communications (URLLC) traffic with strict requirements on latency and reliability. The URLLC...
Preprint
Vital signs including heart rate, respiratory rate, body temperature and blood pressure, are critical in the clinical decision making process. Effective early prediction of vital signs help to alert medical practitioner ahead of time and may prevent adverse health outcomes. In this paper, we suggest a new approach called generative boosting, in ord...
Article
Full-text available
A compact, light-weight and low-power wireless vital signs monitoring system based on Wireless Body Area Network (WBAN) protocol has been developed. The system, VySys, includes two compact wearable wireless biosensor devices for continuous vital signs capturing and transmission, a gateway to relay the message collected from the biosensors to cloud,...
Article
Practical energy harvesting (EH) based communication systems typically use a battery to temporarily store the harvested energy prior to its use for communication. The battery capacity can quickly degrade with time if it is subject to repeated shallow charge-discharge cycles. This motivates the cycle constraint which mandates that a battery must be...
Article
We consider a multiple-access channel (MAC), where transmitters are powered by energy harvesting. They are equipped with batteries having non-ideal charging and discharging characteristics, resulting in a fractional loss of power driven into or drawn from them. Assuming that each user consumes constant power for circuit operation during transmissio...
Article
Full-text available
Run-length limited (RLL) codes are a well-studied class of constrained codes having application in diverse areas, such as optical and magnetic data recording systems, DNA-based storage, and visible light communication. RLL codes have also been proposed for the emerging area of simultaneous energy and information transfer, where the receiver uses th...
Article
Motivated by the idea of “transmitting energy and information simultaneously”, we investigate, in this paper, the impact of constraints on the amount of energy that individual symbols carry, i.e., minimum amplitude constraints. We consider a Gaussian mixture noise channel with both minimum and peak amplitude constraints. First, we prove that the ca...
Article
We consider the lossy transmission of a single source over parallel additive white Gaussian noise channels with independent quasi-static fading, which we term the lossy multiconnectivity problem.We assume that only the decoder has access to the channel state information. Motivated by ultra-reliable and low latency communication requirements, we are...
Article
Motivated by real-world machine learning applications, we analyse approximations to the non-asymptotic fundamental limits of statistical classification. In the binary version of this problem, given two training sequences generated according to two unknown distributions |$P_1$| and |$P_2$|⁠, one is tasked to classify a test sequence that is known to...
Article
In the real-world, it is virtually impossible to have non-causal knowledge of future events. Research in energy harvesting (EH) systems that assumes knowledge of future energy arrivals falls short in terms of practical utility, pointing to the need for online strategies. In addition, the modeling and analysis for EH transmitter and receiver are inh...
Preprint
Full-text available
We apply the generalized sphere-packing bound to two classes of subblock-constrained codes. A la Fazeli et al. (2015), we made use of automorphism to significantly reduce the number of variables in the associated linear programming problem. In particular, we study binary constant subblock-composition codes (CSCCs), characterized by the property tha...
Article
Tandon and Ulukus (2011) gave an outer bound on the capacity region of the two-user Gaussian multiple access channel (MAC) with noisy feedback based on the idea of dependence balance (DB). This outer bound is described using a covariance matrix with three independent parameters. In this paper, we simplify their results and express the DB based oute...
Preprint
Feature selection, which searches for the most representative features in observed data, is critical for health data analysis. Unlike feature extraction, such as PCA and autoencoder based methods, feature selection preserves interpretability, meaning that the selected features provide direct information about certain health conditions (i.e., the la...
Preprint
Full-text available
Run-length limited (RLL) codes are a well-studied class of constrained codes having application in diverse areas such as optical and magnetic data recording systems, DNA-based storage, and visible light communication. RLL codes have also been proposed for the emerging area of simultaneous energy and information transfer, where the receiver uses the...
Article
Analysing patients' health data using machine learning techniques can improve both patient outcomes and hospital operations. However, heterogeneous patient data (e.g., vital signs) and inefficient feature learning methods affect the implementation of machine learning-based patient data analysis. In this paper, we present a novel unsupervised Deep l...
Preprint
Communication systems for multicasting information and energy simultaneously to more than one user are investigated. In the system under study, a transmitter sends the same message and signal to multiple receivers over distinct and independent channels. In this setting, results for compound channels are applied to relate the operational compound ca...
Preprint
Full-text available
We consider the lossy transmission of a single source over parallel additive white Gaussian noise channels with independent quasi-static fading, which we term as the lossy multi-connectivity problem. We assume that only the decoder has access to the channel state information. Motivated by ultra-reliable and low latency communication requirements, w...
Preprint
Full-text available
Motivated by real-world machine learning applications, we analyze approximations to the non-asymptotic fundamental limits of statistical classification. In the binary version of this problem, given two training sequences generated according to two {\em unknown} distributions $P_1$ and $P_2$, one is tasked to classify a test sequence which is known...
Article
Graphical models have been widely applied in distributed network computation problems such as inference in large-scale sensor networks. While belief propagation (BP) based on message passing is a powerful approach to solving such distributed inference problems, one major challenge, in the context of wireless sensor networks, is how to systematicall...
Preprint
Full-text available
In this paper, we consider an end-to-end communication system with an energy-harvesting receiver. The receiver has a time-switching architecture and can harvest energy from both a dedicated transmitter and other ambient radio-frequency (RF) sources. A scheme called Harvest-then-Receive is used, in which the receiver first harvests energy, then rece...
Article
Internet of Things (IoT) systems will increasingly rely on energy harvested from their environment, and energy harvesting (EH) techniques necessitate a rethinking of how we design and optimize IoT systems. The performance of EH IoT systems is affected by the battery non-idealities and the energy consumption for transmitting and receiving. While EH...
Article
Full-text available
We consider a multiple-access channel where the users are powered from batteries having non-negligible internal resistance. When power is drawn from the battery, a variable fraction of the power, which is a function of the power drawn from the battery, is lost across the internal resistance. Hence, the power delivered to the load is less than the p...
Article
Full-text available
We consider an energy harvesting transmitter equipped with two batteries having finite storage capacities, communicating over an additive white Gaussian channel. The work is motivated by an observation that many practical batteries, when repeatedly charged after being partially discharged, suffer from degradation in the usable capacity. The capacit...
Article
Full-text available
We consider a universal joint source channel coding (JSCC) scheme to transmit an arbitrary memoryless source over an arbitrary additive channel. We adopt an architecture that consists of Gaussian codebooks for both the source reproduction sequences and channel codewords. The natural minimum Euclidean distance encoder and decoder, however, need to b...
Article
Constrained coding is used widely in digital communication and storage systems. In this paper, we study a generalized sliding window constraint called the skip-sliding window. A skip-sliding window (SSW) code is defined in terms of the length $L$ of a sliding window, skip length $J$, and cost constraint $E$ in each sliding window. Each valid codewo...
Article
The difficulty of modeling energy consumption in communication systems leads to challenges in energy harvesting (EH) systems, in which nodes scavenge energy from their environment. An EH receiver must harvest enough energy for demodulating and decoding. The energy required depends upon factors, like code rate and signal-to-noise ratio, which can be...
Article
In this paper, we optimize an energy harvesting transmitter, communicating over a slow fading channel, using layered coding. The transmitter has access to the channel statistics, but does not know the exact channel state. In layered coding, the codewords are first designed for a given finite set of channel states at different rates, and then the co...
Article
The analysis and optimization of energy-harvesting transmitters and receivers are different. This paper considers an end-to-end communication with an energy-harvesting receiver. The receiver has a time-switching architecture and can harvest energy from both a dedicated transmitter and other ambient radio-frequency (RF) sources. We first argue that...
Conference Paper
Predictive diagnosis benefits both patients and hospitals. Major challenges limiting the effectiveness of machine learning based predictive diagnosis include the lack of efficient feature selection methods and the heterogeneity of measured patient data (e.g., vital signs). In this paper, we propose DLFS, an efficient feature selection scheme based...
Article
Full-text available
In this paper, we revisit two multi-terminal lossy source coding problems: the lossy source coding problem with side information available at the encoder and one of the two decoders, which we term as the Kaspi problem (Kaspi, 1994), and the multiple description coding problem with one semi-deterministic distortion measure, which we refer to as the...
Article
Full-text available
The rate-distortion saddle-point problem considered by Lapidoth (1997) consists in finding the minimum rate to compress an arbitrary ergodic source when one is constrained to use a random Gaussian codebook and minimum (Euclidean) distance encoding is employed. We extend Lapidoth's analysis in several directions in this paper. Firstly, we consider r...
Article
Full-text available
In this paper, we revisit the high-dimensional content identification with lossy recovery problem (Tuncel and G\"und\"uz, 2014). We first present a non-asymptotic converse bound. Invoking the non-asymptotic converse bound, we derive a lower bound on the exponent of the probability of correct decoding (the strong converse exponent) and show the lowe...
Article
Full-text available
Due to stringent constraints on resources, it may be infeasible to acquire the current channel state information at the transmitter in energy harvesting communication systems. In this paper, we optimize an energy harvesting transmitter, communicating over a slow fading channel, using layered coding. The transmitter has access to the channel statist...
Article
Full-text available
The study of subblock-constrained codes has recently gained attention due to their application in diverse fields. We present bounds on the size and asymptotic rate for two classes of subblock-constrained codes. The first class is binary constant subblock-composition codes (CSCCs), where each codeword is partitioned into equal sized subblocks, and e...
Article
Modern systems will increasingly rely on energy harvested from their environment. Such systems utilize batteries to smoothen out the random fluctuations in harvested energy. These fluctuations induce highly variable battery charge and discharge rates, which affect the efficiencies of practical batteries that typically have non-zero internal resista...
Article
We study the application of polar codes in deletion channels by analyzing the cascade of a binary erasure channel (BEC) and a deletion channel. We show how polar codes can be used effectively on a BEC with a single deletion, and propose a list decoding algorithm with a cyclic redundancy check for this case. The decoding complexity is $O(N^2\log N)$...
Article
We consider multi-source energy harvesting communication systems, where the energy harvested from two independent processes is used for the transmission of the data packets. The data packets arrive randomly and wait in a queue for accumulation of sufficient energy and for service completion of previously arrived packets. Thus, the data queue dynami...
Article
Transmission in the 60 GHz frequency band performs poorly in long-distance direct links due to the large path loss. The received signal strength can be relatively weak if the line-of-sight path is blocked by obstacles. A device cooperation approach, which effectively combats the severe path loss thereby improving the overall throughput for wireless...
Article
In this paper, we consider the problem of blockwise streaming compression of a pair of correlated sources, which we term streaming Slepian-Wolf coding. We study the moderate deviations regime in which the rate pairs of a sequence of codes converges, along a straight line, to various points on the boundary of the Slepian-Wolf region at a speed slowe...