R. Venkatesha Prasad

Cognitive radio emergency networks - requirements and design

Currently deployed wireless emergency networks possess low spectrum efficiency, similar to their civilian wireless counterparts. Its due to the traditional radio frequency partitioning where each service has uniquely assigned bandwidth. To alleviate the problem one can propose dynamic channel assignment as a promising foundation for physical and link layer design of future wireless emergency communication networks. Here we identify functional requirements and system specifications for mobile ad hoc emergency networks built on top of cognitive radio. We also propose a simple Cognitive Radio medium access control protocol applicable to our network model, adopted from distributed channel assignment algorithm of IEEE 802.11

Fairness in Wireless Networks:Issues, Measures and Challenges

The pervasiveness of wireless technology has indeed created massive opportunity to integrate almost everything into the Internet fabric. This can be seen with the advent of Internet of Things and Cyber Physical Systems, which involves cooperation of massive number of intelligent devices to provide intelligent services. Fairness amongst these devices is an important issue that can be analysed from several dimensions, e.g., energy usage, achieving required quality of services, spectrum sharing, and so on. This article focusses on these viewpoints while looking at fairness research. To generalize, mainly wireless networks are considered. First, we present a general view of fairness studies, and pose three core questions that help us delineate the nuances in defining fairness. Then, the existing fairness models are summarized and compared. We also look into the major fairness research domains in wireless networks such as fair energy consumption control, power control, topology control, link and flow scheduling, channel assignment, rate allocation, congestion control and routing protocols. We make a distinction amongst fairness, utility and resource allocation to begin with. Later, we present their inter-relation. At the end of this article, we list the common properties of fairness and give an example of fairness management. Several open research challenges that point to further work on fairness in wireless networks are also discussed. Indeed, the research on fairness is entangled with many other aspects such as performance, utility, optimization and throughput at the network and node levels. While consolidating the contributions in the literature, this article tries to explain the niceties of all these aspects in the domain of wireless networking.

Comparison of voice activity detection algorithms for VoIP

We discuss techniques for voice activity detection (VAD) for voice over Internet Protocol (VoIP). VAD aids in saving the bandwidth requirement of a voice session, thereby increasing the bandwidth efficiently. We compare the quality of speech, level of compression and computational complexity for three time-domain and three frequency-domain VAD algorithms. Implementation of time-domain algorithms is computationally simple. However, better speech quality is obtained with the frequency-domain algorithms. A comparison of the merits and demerits along with the subjective quality of speech after removal of silence periods is presented for all the algorithms. A quantitative measurement of speech quality for different algorithms is also presented.

IEEE 802.11ah: Advantages in standards and further challenges for sub 1 GHz Wi-Fi

The rapid developments in Internet-of-Things (IoT) and Machine-to-Machine (M2M) communication make it necessary to design communication systems operating in different wireless spectrum as an alternative to highly congested wireless access systems. In addition, the deployment of wireless smart meter devices is ramping up and it is expected that such devices will flood the market in the near future competing for the same wireless spectrum. The IEEE 802.11ah standardization task group is developing a global Wireless LAN (WLAN) standard that will allow wireless access using carrier frequencies below 1 GHz in the ISM (Industrial, Scientific, and Medical) band and will help Wi-Fi-enabled devices to get guaranteed access for short-burst data transmissions, such as meter data. In addition to exploiting the underutilized sub 1 GHz spectrum the improved coverage range allows new applications to emerge such as wide area based sensor networks, sensor backhaul systems and potential Wi-Fi off-loading functions. This paper summarizes the IEEE 802.11ah standardization activities in progress and discusses advantages and challenges in the design of physical layer (PHY) and media access control (MAC) schemes in the sub 1 GHz band.

Radio-over-Fiber based architecture for seamless wireless indoor communication in the 60GHz band

In order to satisfy the increasing demand of wireless broadband multimedia services, much attention has been paid to the 60GHz band where as much as 5GHz of spectrum has been reserved. However, in the indoor environment, the propagation of signals at this millimeter wave band is strongly hindered by walls, people and their movement, furniture, etc. As a result, a mobile user might experience frequent loss of connection as the user moves from one cell to another. In this paper, we propose a flexible and cost-effective Radio-over-Fiber (RoF) based network architecture to support indoor networking at millimeter wave bands. To create sufficient overlap areas between cells and thus to ensure a seamless communication environment for mobile users, the concept of Extended Cell is introduced. We demonstrate the effectiveness of the proposed architecture with a detailed simulation study of an indoor scenario. Furthermore, we analyze the impact of the architecture on the performance of two popular state-of-the-art protocols, namely IEEE 802.11 and IEEE 802.16, to find which Medium Access Control (MAC) protocol is suitable for RoF networks.

Beam switching support to resolve link-blockage problem in 60 GHz WPANs

In this paper, we propose a solution to resolve link blockage problem in 60 GHz WPANs. Line-of-Sight (LOS) link is easily blocked by a moving person, which is concerned as one of the severe problems in 60 GHz systems. Beamforming is a feasible technique to resolve link blockage by switching the beam path from LOS link to a Non-LOS (NLOS) link. We propose and evaluate two kinds of Beam Switching (BS) mechanisms: instant decision based BS and environment learning based BS. We examine these mechanisms in a typical indoor WPAN scenario. Extensive simulations have been carried out, and our results reveal that combining angle-of-arrival with the received signal to noise ratio could make better decision for beam switching. Our work provides valuable observations for beam switching during point-to-point communication using 60 GHz radio.

Energy-Efficient Reliable Routing Considering Residual Energy in Wireless Ad Hoc Networks

We propose two novel energy-aware routing algorithms for wireless ad hoc networks, called reliable minimum energy cost routing (RMECR) and reliable minimum energy routing (RMER). RMECR addresses three important requirements of ad hoc networks: energy-efficiency, reliability, and prolonging network lifetime. It considers the energy consumption and the remaining battery energy of nodes as well as quality of links to find energy-efficient and reliable routes that increase the operational lifetime of the network. RMER, on the other hand, is an energy-efficient routing algorithm which finds routes minimizing the total energy required for end-to-end packet traversal. RMER and RMECR are proposed for networks in which either hop-by-hop or end-to-end retransmissions ensure reliability. Simulation studies show that RMECR is able to find energy-efficient and reliable routes similar to RMER, while also extending the operational lifetime of the network. This makes RMECR an elegant solution to increase energy-efficiency, reliability, and lifetime of wireless ad hoc networks. In the design of RMECR, we consider minute details such as energy consumed by processing elements of transceivers, limited number of retransmissions allowed per packet, packet sizes, and the impact of acknowledgment packets. This adds to the novelty of this work compared to the existing studies.

Reincarnation in the Ambiance: Devices and Networks with Energy Harvesting

Miniaturization of devices with higher computational capacity coupled with advancement in communication technologies is driving the growth of deployment of sensors and actuators in our surroundings. To keep up the pace with this growth, these tiny, battery-powered devices need small-sized and high-energy density batteries for longer operational time, which calls for improvement in battery technologies. An alternative is to harvest energy from the environment. An important aspect of energy harvesting is that the devices go through birth and death cycles with respect to their power unlike battery powered ones. Another important aspect is that contextual information is also generated while devices harvest energy from their ambiance. In this article we provide a comprehensive study of various types of energy harvesting techniques. We then provide some models used in energy harvesting systems and the design of such systems. We also throw light on the power management and networking aspects of the energy harvesting devices. At the end we discuss the major issues and avenues for further research.

DIAT: A Scalable Distributed Architecture for IoT

The advent of Internet of Things (IoT) has boosted the growth in number of devices around us and kindled the possibility of umpteen number of applications. One of the major challenges in the realization of IoT applications is interoperability among various IoT devices and deployments. Thus, the need for a new architecture-comprising smart control and actuation-has been identified by many researchers. In this paper, we propose a Distributed Internet-like Architecture for Things (DIAT), which will overcome most of the obstacles in the process of large-scale expansion of IoT. It specifically addresses heterogeneity of IoT devices, and enables seamless addition of new devices across applications. In addition, we propose an usage control policy model to support security and privacy in a distributed environment. We propose a layered architecture that provides various levels of abstraction to tackle the issues such as scalability, heterogeneity, security, and interoperability. The proposed architecture is coupled with cognitive capabilities that helps in intelligent decision-making and enables automated service creation. Using a comprehensive use-case, comprising elements from multiple-application domains, we illustrate the usability of the proposed architecture.

A scalable distributed architecture towards unifying IoT applications

The advent of Internet of Things (IoT) has kindled the possibility of umpteen number of applications. One of the major challenges in the realization of IoT applications is interoperability among various IoT entities. Thus, the need for a new architecture - comprising of smart control and actuation - has been identified by many researchers. In this article, we propose a distributed, interoperable architecture for IoT, which will overcome most of the obstacles in the process of large scale expansion of IoT. It specifically addresses heterogeneity of IoT devices, and enables seamless addition of new devices across applications. We propose a layered architecture that provides various levels of abstraction to tackle the issues such as, scalability, heterogeneity and interoperability. Using a comprehensive study of a use-cases, comprising elements from multiple-application domains, we illustrate the usability of the proposed architecture.