Swaminathan Ramabadran

Indian Institute of Technology Indore | IITI · Department of Electrical Engineering

This article addresses the Gaussian filtering problem under the environment of jointly occurring delayed and missing measurements. In this work, the former irregularity is incorporated (in the measurement model) using a Bernoulli random variable (BRV) and a geometric random variable, while the latter is subsumed with the help of the BRV; thereby, i...

Free space optics communication (FSO) offers several advantages over its counterpart radio frequency (RF) systems in terms of bandwidth, data rates, and cost efficiency. However, FSO, being a line-of-sight (LoS) communication system, is hindered by various environmental factors. In this paper, we propose a multihop decode-and-forward (DF) relaying-...

Gaussian filtering traditionally suffers from two major drawbacks: i) Gaussian approximation of the intrinsic non-Gaussian measurement noises and ii) ignoring delay in measurements. This paper designs an advanced Gaussian filtering algorithm for addressing the two drawbacks and improving the accuracy. The proposed method is abbreviated as GFMCFD, i...

Recently, the use of reconfigurable intelligent surfaces (RIS) has gained popularity and is emerging as a promising technique to provide improved link reliability and enhanced coverage area. In this paper, we propose an optical reflecting surface (ORS)-assisted free space optics (FSO) communication system, which is based on optical space shift keyi...

Unmanned-aerial-vehicle (UAV)-based communications are expected to play an important role in the future generation wireless communication networks. It is a promising solution to enhance the wireless connectivity of devices without infrastructure. As compared to the terrestrial communications, UAVs offer various advantages such as line-of-sight (LoS...

Free space optics (FSO) communication due to its large optical carrier bandwidth offers better data rates close to gigabits per second (GBPS) compared to radio frequency (RF) communication and can support seamless ubiquitous high-speed broadband connectivity, which is a significant requirement for sixth-generation (6G) communication. It is also env...

Recently, generalized fading distributions have gained substantial research interest due to their applicability and adaptability in practical scenarios. In this paper, we derive the exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the maximal-ratio combining (MRC) of the free spa...

Particle filtering is probably the most widely accepted methodology for general nonlinear filtering applications. The performance of a particle filter critically depends on the choice of proposal distribution. In this paper, we propose using a wrapped normal distribution as a proposal distribution for angular data, i.e . data within finite range (-...

In this paper, we study the physical layer security performance of a downlink space-air-ground integrated network (SAGIN), where a satellite communicates with the ground user/destination via a high-altitude platform station (HAPS)- based relay in the presence of an eavesdropper. In particular, we propose to use hybrid free space optical (FSO)/radio...

This paper investigates the ergodic capacity performance of hybrid free space optics (FSO)/ radio frequency (RF) system by employing an adaptive-combining-based switching scheme. In the adaptive combining scheme, the FSO and RF links are combined using the maximal-ratio combining (MRC) at the output, when the instantaneous signal-to-noise ratio (SN...

Free-space optics (FSO) communication is often unreliable, especially for long distances, as it suffers from attenuation due to foggy weather, atmospheric turbulence, and pointing errors. To avoid communication link failure, radio frequency (RF) communication, which is unaffected from these effects, is utilized when FSO communication is in outage....

Coulomb oscillator is used for analyzing several real-life systems, which demand a precise modeling of the oscillation. The modeling is based on the stochastic estimation of unknown parameters of the model representing the oscillation. This paper introduces a Bayesian approach for the estimation of unknown parameters from sensor-generated noisy dat...

In recent years, a growing interest has been witnessed in the usage of free space optics (FSO) link for satellite communication (SATCOM) scenarios, as it offers much higher data rates up to gigabits per second (Gbps) compared to existing radio frequency (RF) link. However, FSO links are sensitive to beam scintillation and pointing errors. In this p...

Optical wireless communication (OWC) has garnered significant importance to provide gigabit capacity links owing to its unique features. Free-space optics (FSO) communication, which is the term used for OWC in an outdoor scenario, is a good candidate to establish ground-to-satellite/satellite-to-ground links. Despite of many advantages, FSO communi...

Hybrid free space optics/radio frequency (FSO/RF) communication has been considered as a promising solution for reliable wireless backhaul connectivity for 5G and beyond wireless communication systems. In this paper, comprehensive performance analysis of the hybrid FSO/RF system has been carried out considering single-threshold-based switching stra...

This study investigates the performance of a decode‐and‐forward‐relay‐based hybrid free space optical (FSO)/radio frequency (RF) system with selection combining. The proposed hybrid system considers an FSO sub‐system as a default transmission option and RF sub‐system is utilised when FSO is in outage. For the proposed system, the outage threshold s...

This study deals with the performance analysis of adaptive combining‐based hybrid free‐space optics (FSO)/radio‐frequency (RF) system in a terrestrial communication scenario with and without pointing errors. Here, outage probability and average symbol error rate (SER) are used as the performance metrics. Adaptive combining is a switching scheme in...

Product codes are multidimensional codes constructed using multiple component codes. In this paper, novel algorithms are proposed for the blind estimation of twodimensional product code parameters over noisy channel conditions considering Reed-Solomon (RS) and Bose-Chaudhuri-Hocquenghem (BCH) as component codes. The performance of the algorithms in...

Blind estimation of forward error correction code parameters at the receiver plays a significant role in non-cooperative communication, adaptive modulation and coding systems, and reconfigurable receiver systems. Turbo convolutional codes, a parallel concatenation of multiple convolutional codes, are used in digital communication and storage system...

The performance of a free space optics (FSO) transmission suffers from the atmospheric turbulence and the attenuation in foggy environment. By employing relay nodes, the error rate and the coverage area of the FSO communication system can be significantly improved. However, the pointing errors, generated because of the building sway, have the poten...

In this paper, we propose a switching scheme for a hybrid free-space optical (FSO)/radio frequency (RF) system with a selective decode-and-forward (DF) relay network. Specifically, the system transmits over FSO channels when the instantaneous signal-to-noise ratio (SNR) at the FSO receiver is greater than the threshold SNR. If the SNR drops below t...

Blind reconstruction of channel coding parameters plays a significant role in non-cooperative military and spectrum surveillance applications. Further, it also gives additional advantages in applications such as cognitive radio, adaptive modulation and coding, and so on. In this study, blind estimation algorithms are proposed to identify code dimen...

Blind estimation of code and interleaver parameters is useful in smart storage systems and ubiquitous communication applications such as adaptive modulation and coding, reconfigurable radio systems, non-cooperative radio systems, etc. In this paper, we analyze Reed-Solomon (RS) encoded data stream and propose blind estimation algorithms to identify...

A novel algorithm has been proposed for the blind estimation of two-dimensional turbo product code (TPC) parameters over noisy channel conditions. The performance of the algorithm is investigated for different code dimension values.

Presentation

Forward error correction (FEC) codes followed by an interleaver play a significant role in improving the error performance of the digital systems by counteracting random and burst errors. In most of the applications, interleaver and FEC code parameters are known at the receiver to successfully de-interleave and decode the information bits. However,...

In data communication and digital storage applications, interleaver, which rearranges the encoded data stream, follows the channel encoder to prevent burst errors. In general, forward error correction (FEC) codes provide protection against randomly distributed errors, whereas interleaver provides protection against error bursts. To de-interleave th...

Cooperative diversity systems with optimal and suboptimal antenna and relay selection have acquired significant attention for more than half a decade. However, optimal antenna and relay selection strategies require global channel state information (CSI), which is a cumbersome process. In this paper, we propose a diversity optimal and three suboptim...

IEEE PIMRC 2016 Presentation

Selection combining (SC) with full channel state information (CSI) achieves full diversity order in a decode-and-forward (DF) relaying system. However, the estimation of CSI of all the links is a cumbersome process. As an alternative, switched-diversity techniques have been proposed in the literature, in which CSI of all the links are not simultane...

Cooperative diversity system improves the communication reliability and throughput in a multipath fading environment with the help of relay nodes. We consider a cooperative diversity system with a source (S), a decode and forward (DF) relay (R), and a selection combining (SC) enabled destination (D). In this paper, we derive the exact end-to-end sy...

In this letter, an uncoded cooperative diversity system with a source, two decode-and-forward (DF) relays, and a destination (D) is considered. We propose a hybrid selection and switch-and-stay combining (HSSSC) scheme at D. Furthermore, we also derive the exact symbol error probability (SEP) of this scheme for DF relaying over slow and flat Raylei...

In this letter, we consider an uncoded cooperative diversity system consisting of a source (S), a decode and forward (DF) relay (R), and a destination (D). We assume slow, flat, and correlated Nakagami-m fading environment and employ selection combining (SC) at D. Furthermore, we derive the exact end-to-end symbol error probability (SEP) of this sy...

The current scenario of transportation infrastructure demands the need for developing efficient intelligent transportation systems (ITS) because of the increased population, changes in population density, traffic congestion, etc. Recent literature on ITS discuss on the need for green cooperative diversity techniques to improve the energy efficiency...

In this paper, we analyse the performance of a single-relay cooperative diversity system, which is an effective technique to combat the effects of small scale fading, in a more realistic scenario by assuming a correlation among source-to-relay (SR), relay-to-destination (RD), and source-to-destination (SD) links. A generalised closed form end-to-en...

Cooperative communication plays a vital role in improving the error performance and throughput of a communication system. In this paper, we consider a cooperative diversity system with a source (S), a relay (R) and a destination (D). The major contribution of this paper is two fold: (1) closed form symbol error probability (SEP) expression has been...

Cooperative diversity is a viable technique to improve the communication reliability and the system throughput. We consider a system comprising of a source (S), a relay (R) and a destination (D). Relay cooperation is achieved through decode and forward protocol. A realistic scenario which considers correlation between SD and RD links is a hardly de...

With the rapid growth of wireless communication in recent years, the need for high speed data transmission is increased. Orthogonal Frequency Division Multiplexing (OFDM) is a promising candidate for achieving high data rates in mobile environment because of its multicarrier modulation technique and ability to convert a frequency selective fading c...