arXiv subjects

Vasuki Narasimha Swamy

Publications and source records attributed to Vasuki Narasimha Swamy.

7 recordsLinked to original sources

arXiv2021

Connection Management xAPP for O-RAN RIC: A Graph Neural Network and Reinforcement Learning Approach

Connection management is an important problem for any wireless network to ensure smooth and well-balanced operation throughout. Traditional methods for connection management (specifically user-cell association) consider sub-optimal and greedy solutions such as connection of each user to a cell with maximum receive power. However, network performance can be improved by leveraging machine learning (ML) and artificial intelligence (AI) based solutions. The next generation software defined 5G networks defined by the Open Radio Access Network (O-RAN) alliance facilitates the inclusion of ML/AI based solutions for various network problems. In this paper, we consider intelligent connection management based on the O-RAN network architecture to optimize user association and load balancing in the network. We formulate connection management as a combinatorial graph optimization problem. We propose a deep reinforcement learning (DRL) solution that uses the underlying graph to learn the weights of the graph neural networks (GNN) for optimal user-cell association. We consider three candidate objective functions: sum user throughput, cell coverage, and load balancing. Our results show up to 10% gain in throughput, 45-140% gain cell coverage, 20-45% gain in load balancing depending on network deployment configurations compared to baseline greedy techniques.

cs.IT↗

arXiv2018

Wireless Channel Dynamics and Robustness for Ultra-Reliable Low-Latency Communications

Interactive, immersive and critical applications demand ultra-reliable low-latency communication (URLLC). To build wireless communication systems that can support these applications, understanding the characteristics of the wireless medium is paramount. Although wireless channel characteristics and dynamics have been extensively studied, it is important to revisit these concepts in the context of the strict demands of low latency and ultra-reliability. In this paper, we bring a modeling approach from robust control to wireless communication -- the wireless channel characteristics are given a nominal model around which we allow for some quantified uncertainty. We propose certain key "directions" along which to bound model uncertainty that are relevant to URLLC. For the nominal model, we take an in-depth look at wireless channel characteristics such as spatial and temporal correlations based on Jakes' model. Contrary to what has been claimed in the literature, we find that standard Rayleigh fading processes are not bandlimited. This has significant implications on the predictability of channels. We also find that under reasonable conditions the spatial correlation of channels provide a fading distribution that is not too far off from an independent spatial fading model. Additionally, we look at the impact of these channel models on cooperative communication based systems. We find that while spatial-diversity-based techniques are necessary to combat the adverse effects of fading, time-diversity-based techniques are necessary to be robust against unmodeled errors. Robust URLLC systems need to operate with both an SNR margin and a time/repetition margin.

cs.IT↗

arXiv2018

Network Coding for Real-time Wireless Communication for Automation

Real-time applications require latencies on the order of a millisecond with very high reliabilities, paralleling the requirements for high-performance industrial control. Current wireless technologies like WiFi, Bluetooth, LTE, etc. are unable to meet these stringent latency and reliability requirements, forcing the use of wired systems. This paper introduces a wireless communication protocol based on network coding that in conjunction with cooperative communication techniques builds the necessary diversity to achieve the target reliability. The proposed protocol is analyzed using a communication theoretic delay-limited-capacity framework and compared to proposed protocols without network coding. The results show that for larger network sizes or payloads employing network coding lowers the minimum SNR required to achieve the target reliability. For a scenario inspired by an industrial printing application with $30$ nodes in the control loop, aggregate throughput of $4.8$ Mb/s, $20$MHz of bandwidth and cycle time under $2$ ms, the protocol can robustly achieve a system probability of error better than $10^{-9}$ with a nominal SNR less than $2$ dB under ideal channel conditions.

cs.IT↗

arXiv2017

Real-time Cooperative Communication for Automation over Wireless

High-performance industrial automation systems rely on tens of simultaneously active sensors and actuators and have stringent communication latency and reliability requirements. Current wireless technologies like WiFi, Bluetooth, and LTE are unable to meet these requirements, forcing the use of wired communication in industrial control systems. This paper introduces a wireless communication protocol that capitalizes on multiuser diversity and cooperative communication to achieve the ultra-reliability with a low-latency constraint. Our protocol is analyzed using the communication-theoretic delay-limited-capacity framework and compared to baseline schemes that primarily exploit frequency diversity. For a scenario inspired by an industrial printing application with thirty nodes in the control loop, 20B messages transmitted between pairs of nodes and a cycle time of $2$ ms, an idealized protocol can achieve a cycle failure probability (probability that any packet in a cycle is not successfully delivered) lower than $10^{-9}$ with nominal SNR below 5 dB in a 20MHz wide channel.

cs.IT↗

arXiv2017

Modeling Actuation Constraints for IoT Applications

Internet of Things (IoT) promises to bring ease of monitoring, better efficiency and innovative services across many domains with connected devices around us. With information from critical parts of infrastructure and powerful cloud-based data analytics, many applications can be developed to gain insights about IoT systems as well as transform their capabilities. Actuation applications form an essential part of these IoT systems, as they enable automation as well as fast low-level decision making. However, modern IoT systems are designed for data acquisition, and actuation applications are implemented in an ad-hoc manner. We identify modeling constraints in a systematic manner as indispensable to support actuation applications because constraints encompass high-level policies dictated by laws of physics, legal policies, user preferences. We explore data models for constraints inIoT system with the example of a home heating system and illustrate the challenges in enforcing these constraints in theIoT system architecture.

eess.SY↗

arXiv2015

Low-Complexity Interactive Algorithms for Synchronization from Deletions, Insertions, and Substitutions

Consider two remote nodes having binary sequences $X$ and $Y$, respectively. $Y$ is an edited version of ${X}$, where the editing involves random deletions, insertions, and substitutions, possibly in bursts. The goal is for the node with $Y$ to reconstruct $X$ with minimal exchange of information over a noiseless link. The communication is measured in terms of both the total number of bits exchanged and the number of interactive rounds of communication. This paper focuses on the setting where the number of edits is $o(\tfrac{n}{\log n})$, where $n$ is the length of $X$. We first consider the case where the edits are a mixture of insertions and deletions (indels), and propose an interactive synchronization algorithm with near-optimal communication rate and average computational complexity of $O(n)$ arithmetic operations. The algorithm uses interaction to efficiently split the source sequence into substrings containing exactly one deletion or insertion. Each of these substrings is then synchronized using an optimal one-way synchronization code based on the single-deletion correcting channel codes of Varshamov and Tenengolts (VT codes). We then build on this synchronization algorithm in three different ways. First, it is modified to work with a single round of interaction. The reduction in the number of rounds comes at the expense of higher communication, which is quantified. Next, we present an extension to the practically important case where the insertions and deletions may occur in (potentially large) bursts. Finally, we show how to synchronize the sources to within a target Hamming distance. This feature can be used to differentiate between substitution and indel edits. In addition to theoretical performance bounds, we provide several validating simulation results for the proposed algorithms.

cs.IT↗

arXiv2013

An asymptotically optimal push-pull method for multicasting over a random network

We consider allcast and multicast flow problems where either all of the nodes or only a subset of the nodes may be in session. Traffic from each node in the session has to be sent to every other node in the session. If the session does not consist of all the nodes, the remaining nodes act as relays. The nodes are connected by undirected links whose capacities are independent and identically distributed random variables. We study the asymptotics of the capacity region (with network coding) in the limit of a large number of nodes, and show that the normalized sum rate converges to a constant almost surely. We then provide a decentralized push-pull algorithm that asymptotically achieves this normalized sum rate without network coding.

cs.IT↗