Wireless Communications

The smart grid is conceived of as an electric grid that can deliver electricity in a controlled, smart way from points of generation to active consumers. Demand response (DR), by promoting the interaction and responsiveness of the customers, may offer a broad range of potential benefits on system operation and expansion and on market efficiency. Moreover, by improving the reliability of the power system and, in the long term, lowering peak demand, DR reduces overall plant and capital cost investments and postpones the need for network upgrades. In this paper a survey of DR potentials and benefits in smart grids is presented. Innovative enabling technologies and systems, such as smart meters, energy controllers, communication systems, decisive to facilitate the coordination of efficiency and DR in a smart grid, are described and discussed with reference to real industrial case studies and research projects.

Demand response and smart grids—A survey

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, equipped with the intrinsic capabilities of the cognitive radio, will provide an ultimate spectrum-aware communication paradigm in wireless communications. CR networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse quality-of-service (QoS) requirements. Specifically, in cognitive radio ad hoc networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this paper, intrinsic properties and current research challenges of the CRAHNs are presented. First, novel spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. A particular emphasis is given to distributed coordination between CR users through the establishment of a common control channel. Moreover, the influence of these functions on the performance of the upper layer protocols, such as the network layer, and transport layer protocols are investigated and open research issues in these areas are also outlined. Finally, a new direction called the commons model is explained, where CRAHN users may independently regulate their own operation based on pre-decided spectrum etiquette.

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CRAHNs: Cognitive radio ad hoc networks

2005년 대한 생화학·분자생물학회 하계학술대회를 다녀와서

In this paper, different control channel (CC) implementations for multichannel medium access control (MAC) algorithms are compared and analyzed in the context of opportunistic spectrum access (OSA) as a function of spectrum-sensing performance and licensed user activity. The analysis is based on a discrete Markov chain model of a subset of representative multichannel OSA MAC classes that incorporates physical layer effects, such as spectrum sensing and fading. The analysis is complemented with extensive simulations. The major observations are given as follows: 1) When the CC is implemented through a dedicated channel, sharing such dedicated channel with the licensed user does not significantly decrease the throughput achieved by the OSA network when the data packet sizes are sufficiently large or the number of considered data channels is small. 2) Hopping OSA MACs, where the CC is spread over all channels, are less susceptible to licensed user activity than those with a dedicated CC (in terms of both average utilization and on/off times). 3) Scanning efficiency has a large impact on the achievable performance of licensed and OSA users for all analyzed protocols. 4) The multiple rendezvous MAC class, which has yet to be proposed in OSA literature, outperforms all the multichannel MAC designs analyzed in this paper.

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Performance Analysis of Multichannel Medium Access Control Algorithms for Opportunistic Spectrum Access

Narrow-band propagation measurements were conducted at two floors of a multi-storied building at 1.9 GHz to study the behavior of the Rice factor and local mean power. To evaluate the influence of the Rice factor on a pico-cellular system, the outage probability is calculated for two different cases: (i) Rician fading for the desired and interfering signals with different Rice factors; (ii) desired signal with Rician fading and interfering signals with Rayleigh fading with a different local mean power for each interfering signal. Finally, a pico-cellular structure is determined as an illustration. >

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Assessment of a pico-cellular system using propagation measurements at 1.9 GHz for indoor wireless communications

Dynamic Spectrum Access (DSA) radio devices look for temporarily unoccupied frequency bands and attempt to communicate in them. It is envisioned that DSA can substantially increase the capacity of wireless networks by broadening the utilization of radio resources. Given the ubiquitous use of Internet's Transport Control Protocol (TCP), it can be expected that TCP will be used in DSA networks in the future. Whether TCP can efficiently provide stable end-to-end transmissions over DSA links, given their dynamic and unpredictable nature, remained unclear. Therefore, we have studied by simulation the ability of various TCP flavors to efficiently utilize DSA links. We have performed simulations using the TCP stack from the Linux operating system. Our simulations show that modern TCPs can efficiently make use of the dynamic capacity of DSA links for bulk data transmission, under a wide range of conditions, but only if certain requirements are met. We also analytically determine the effect of Primary User (PU) detection errors on TCP performance and conclude that the dominating component responsible for TCP throughput reduction in a DSA environment is the observation time, not, as one might expect, PU detection errors.

Performance of Transport Control Protocol Over Dynamic Spectrum Access Links

In this short note we model the region-wise trends of the evolution to COVID-19 infections using a stochastic SIR model. The SIR dynamics are expressed using \textit{Ito-stochastic differential equations}. We first derive the parameters of the model from the available daily data from European regions based on a 24-day history of infections, recoveries and deaths. The derived parameters have been aggregated to project future trends for the Indian subcontinent, which is currently at an early stage in the infection cycle. The projections are meant to serve as a guideline for strategizing the socio-political counter measures to mitigate COVID-19.

A simple Stochastic SIR model for COVID 19 Infection Dynamics for Karnataka: Learning from Europe

We provide a detailed analytical model for estimating the total energy consumed to exchange a packet over a wireless link. Our model improves many of the current models by considering details such as consumed energy by processing elements of transceivers, packet retransmission, reliability of links, size of data packets and acknowledgments, and also the data rate of wireless links. To develop the model, we use experimental results based on IEEE 802.15.4 devices to show that consumed energy for receiving erroneous packets is comparable to the consumed energy for receiving error-free packets.

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R. V. Prasad

Papers

Performance Analysis of Multichannel Medium Access Control Algorithms for Opportunistic Spectrum Access

Assessment of a pico-cellular system using propagation measurements at 1.9 GHz for indoor wireless communications

Performance of Transport Control Protocol Over Dynamic Spectrum Access Links

A simple Stochastic SIR model for COVID 19 Infection Dynamics for Karnataka: Learning from Europe

An Analytical Energy Consumption Model for Packet Transfer over Wireless Links