Packet-Radio Networks
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A Comparison of Mechanisms for Improving TCP Performance Over Wireless Links
A Comparison of Mechanisms for Improving TCP Performance over Wireless Links Hari Balakrishnan, Venkata N. Padmanabhan, Srinivasan Seshan and Randy H. Katz1 {hari,padmanab,ss,randy}@cs.berkeley.edu Computer Science Division, Department of EECS, University of California at Berkeley Abstract the estimated round-trip delay and the mean linear deviation from it. The sender identifies the loss of a packet either by Reliable transport protocols such as TCP are tuned to per- the arrival of several duplicate cumulative acknowledg- form well in traditional networks where packet losses occur ments or the absence of an acknowledgment for the packet mostly because of congestion. However, networks with within a timeout interval equal to the sum of the smoothed wireless and other lossy links also suffer from significant round-trip delay and four times its mean deviation. TCP losses due to bit errors and handoffs. TCP responds to all reacts to packet losses by dropping its transmission (conges- losses by invoking congestion control and avoidance algo- tion) window size before retransmitting packets, initiating rithms, resulting in degraded end-to-end performance in congestion control or avoidance mechanisms (e.g., slow wireless and lossy systems. In this paper, we compare sev- start [13]) and backing off its retransmission timer (Karn’s eral schemes designed to improve the performance of TCP Algorithm [16]). These measures result in a reduction in the in such networks. We classify these schemes into three load on the intermediate links, thereby controlling the con- broad categories: end-to-end protocols, where loss recovery gestion in the network. is performed by the sender; link-layer protocols, that pro- vide local reliability; and split-connection protocols, that Unfortunately, when packets are lost in networks for rea- break the end-to-end connection into two parts at the base sons other than congestion, these measures result in an station. -
Lecture 8: Overview of Computer Networking Roadmap
Lecture 8: Overview of Computer Networking Slides adapted from those of Computer Networking: A Top Down Approach, 5th edition. Jim Kurose, Keith Ross, Addison-Wesley, April 2009. Roadmap ! what’s the Internet? ! network edge: hosts, access net ! network core: packet/circuit switching, Internet structure ! performance: loss, delay, throughput ! media distribution: UDP, TCP/IP 1 What’s the Internet: “nuts and bolts” view PC ! millions of connected Mobile network computing devices: server Global ISP hosts = end systems wireless laptop " running network apps cellular handheld Home network ! communication links Regional ISP " fiber, copper, radio, satellite access " points transmission rate = bandwidth Institutional network wired links ! routers: forward packets (chunks of router data) What’s the Internet: “nuts and bolts” view ! protocols control sending, receiving Mobile network of msgs Global ISP " e.g., TCP, IP, HTTP, Skype, Ethernet ! Internet: “network of networks” Home network " loosely hierarchical Regional ISP " public Internet versus private intranet Institutional network ! Internet standards " RFC: Request for comments " IETF: Internet Engineering Task Force 2 A closer look at network structure: ! network edge: applications and hosts ! access networks, physical media: wired, wireless communication links ! network core: " interconnected routers " network of networks The network edge: ! end systems (hosts): " run application programs " e.g. Web, email " at “edge of network” peer-peer ! client/server model " client host requests, receives -
Bit & Baud Rate
What’s The Difference Between Bit Rate And Baud Rate? Apr. 27, 2012 Lou Frenzel | Electronic Design Serial-data speed is usually stated in terms of bit rate. However, another oft- quoted measure of speed is baud rate. Though the two aren’t the same, similarities exist under some circumstances. This tutorial will make the difference clear. Table Of Contents Background Bit Rate Overhead Baud Rate Multilevel Modulation Why Multiple Bits Per Baud? Baud Rate Examples References Background Most data communications over networks occurs via serial-data transmission. Data bits transmit one at a time over some communications channel, such as a cable or a wireless path. Figure 1 typifies the digital-bit pattern from a computer or some other digital circuit. This data signal is often called the baseband signal. The data switches between two voltage levels, such as +3 V for a binary 1 and +0.2 V for a binary 0. Other binary levels are also used. In the non-return-to-zero (NRZ) format (Fig. 1, again), the signal never goes to zero as like that of return- to-zero (RZ) formatted signals. 1. Non-return to zero (NRZ) is the most common binary data format. Data rate is indicated in bits per second (bits/s). Bit Rate The speed of the data is expressed in bits per second (bits/s or bps). The data rate R is a function of the duration of the bit or bit time (TB) (Fig. 1, again): R = 1/TB Rate is also called channel capacity C. If the bit time is 10 ns, the data rate equals: R = 1/10 x 10–9 = 100 million bits/s This is usually expressed as 100 Mbits/s. -
X.25: ITU-T Protocol for WAN Communications
X.25: ITU-T Protocol for WAN Communications X.25, an ITU-T protocol for WAN communications, is a packet switched data network protocol which defines the exchange of data as well as control information between a user device, called Data Terminal Equipment (DTE) and a network node, called Data Circuit Terminating Equipment (DCE). X.25 is designed to operate effectively regardless of the type of systems connected to the network. X.25 is typically used in the packet-switched networks (PSNs) of common carriers, such as the telephone companies. Subscribers are charged based on their use of the network. X.25 utilizes a Connection-Oriented service which insures that packets are transmitted in order. X.25 sessions are established when one DTE device contacts another to request a communication session. The DTE device that receives the request can either accept or refuse the connection. If the request is accepted, the two systems begin full-duplex information transfer. Either DTE device can terminate the connection. After the session is terminated, any further communication requires the establishment of a new session. X.25 uses virtual circuits for packets communications. Both switched and permanent virtual circuits are used. X.75 is the signaling protocol for X.25, which defines the signaling system between two PDNs. X.75 is essentially an Network to Network Interface (NNI). X.25 protocol suite comes with three levels based on the first three layers of the OSI seven layers architecture. The Physical Level: describes the interface with the physical environment. There are three protocols in this group: 1) X.21 interface operates over eight interchange circuits; 2) X.21bis defines the analogue interface to allow access to the digital circuit switched network using an analogue circuit; 3) V.24 provides procedures which enable the DTE to operate over a leased analogue circuit connecting it to a packet switching node or concentrator. -
The Beginner's Handbook of Amateur Radio
FM_Laster 9/25/01 12:46 PM Page i THE BEGINNER’S HANDBOOK OF AMATEUR RADIO This page intentionally left blank. FM_Laster 9/25/01 12:46 PM Page iii THE BEGINNER’S HANDBOOK OF AMATEUR RADIO Clay Laster, W5ZPV FOURTH EDITION McGraw-Hill New York San Francisco Washington, D.C. Auckland Bogotá Caracas Lisbon London Madrid Mexico City Milan Montreal New Delhi San Juan Singapore Sydney Tokyo Toronto McGraw-Hill abc Copyright © 2001 by The McGraw-Hill Companies. All rights reserved. Manufactured in the United States of America. Except as per- mitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. 0-07-139550-4 The material in this eBook also appears in the print version of this title: 0-07-136187-1. All trademarks are trademarks of their respective owners. Rather than put a trademark symbol after every occurrence of a trade- marked name, we use names in an editorial fashion only, and to the benefit of the trademark owner, with no intention of infringe- ment of the trademark. Where such designations appear in this book, they have been printed with initial caps. McGraw-Hill eBooks are available at special quantity discounts to use as premiums and sales promotions, or for use in corporate training programs. For more information, please contact George Hoare, Special Sales, at [email protected] or (212) 904-4069. TERMS OF USE This is a copyrighted work and The McGraw-Hill Companies, Inc. -
Evaluating Lora Physical As a Radio Link Technology for Use in a Remote-Controlled Electric Switch System for a Network Bridge
Evaluating LoRa Physical as a Radio Link Technology for use in a Remote-Controlled Electric Switch System for a Network Bridge Radio-Node Abdullahi Aden Hassan / Rasmus Karlsson Källqvist KTH ROYAL INSTITUTE OF TECHNOLOGY ELECTRICAL ENGINEERING AND COMPUTER SCIENCE Acknowledgments We would like to thank our academic mentor Anders Västberg for helping us with the process of writing and carrying through this degree project, answering all of our questions, and for proof reading this report. We would like to thank Amin Azari for showing genuine interest in our project and for answering some math questions we had when calculating the radio link budget, and for discovering that the formula in a book we were using had a printing error which was initially causing our results to be wrong. Thank you to fellow students Michael Henriksson and Sebastian Kullengren for a thorough opposition to this report and for much helpful feedback in keeping the text readable and scientific. Thank you to Björn Pehrson for representing AMPRNet Sweden and giving us the opportunity to work on this project, financing the system prototype and for giving helpful feedback. Finally, we would like to thank program director Bengt Molin for teaching us much of what we know of embedded systems and for lending us equipment used in the development of the hardware prototype. i Abstract This report explores the design of a system for remotely switching electronics on and off within a range of at least 15 km, to be used with battery driven radio nodes for outdoor Wi-Fi network bridging. The application of the network bridges are connecting to remote networks, should Internet infrastructure fail during an emergency. -
Virtual-Circuit Networks: Frame Relay Andatm
CHAPTER 18 Virtual-Circuit Networks: Frame Relay andATM In Chapter 8, we discussed switching techniques. We said that there are three types of switching: circuit switching, packet switching, and message switching. We also men tioned that packet switching can use two approaches: the virtual-circuit approach and the datagram approach. In this chapter, we show how the virtual-circuit approach can be used in wide-area networks. Two common WAN technologies use virtual-circuit switching. Frame Relay is a relatively high-speed protocol that can provide some services not available in other WAN technologies such as DSL, cable TV, and T lines. ATM, as a high-speed protocol, can be the superhighway of communication when it deploys physical layer carriers such as SONET. We first discuss Frame Relay. We then discuss ATM in greater detaiL Finally, we show how ATM technology, which was originally designed as a WAN technology, can also be used in LAN technology, ATM LANs. 18.1 FRAME RELAY Frame Relay is a virtual-circuit wide-area network that was designed in response to demands for a new type ofWAN in the late 1980s and early 1990s. 1. Prior to Frame Relay, some organizations were using a virtual-circuit switching network called X.25 that performed switching at the network layer. For example, the Internet, which needs wide-area networks to carry its packets from one place to another, used X.25. And X.25 is still being used by the Internet, but it is being replaced by other WANs. However, X.25 has several drawbacks: a. -
Kenwood TH-D74A/E Operating Tips
1 Copyrights for this Manual JVCKENWOOD Corporation shall own all copyrights and intellectual properties for the product and the manuals, help texts and relevant documents attached to the product or the optional software. A user is required to obtain approval from JVCKENWOOD Corporation, in writing, prior to redistributing this document on a personal web page or via packet communication. A user is prohibited from assigning, renting, leasing or reselling the document. JVCKENWOOD Corporation does not warrant that quality and functions described in this manual comply with each user’s purpose of use and, unless specifically described in this manual, JVCKENWOOD Corporation shall be free from any responsibility for any defects and indemnities for any damages or losses. Software Copyrights The title to and ownership of copyrights for software, including but not limited to the firmware and optional software that may be distributed individually, are reserved for JVCKENWOOD Corporation. The firmware shall mean the software which can be embedded in KENWOOD product memories for proper operation. Any modifying, reverse engineering, copying, reproducing or disclosing on an Internet website of the software is strictly prohibited. A user is required to obtain approval from JVCKENWOOD Corporation, in writing, prior to redistributing this manual on a personal web page or via packet communication. Furthermore, any reselling, assigning or transferring of the software is also strictly prohibited without embedding the software in KENWOOD product memories. Copyrights for recorded Audio The software embedded in this transceiver consists of a multiple number of and individual software components. Title to and ownership of copyrights for each software component is reserved for JVCKENWOOD Corporation and the respective bona fide holder. -
New Gateways (PDF
Packet Network Notice Rev: 28-Nov-2011 Date: Nov 28, 2011 From: Santa Clara County ARES/RACES Packet Committee Subject: Packet Network Update – New AMPRnet and E-mail gateways Attention: All ECs, AECs, MACs and other Santa Clara County Packet Users This Packet Network Notice contains important information which affects your ability to access and use the county packet backbone. This update covers the following topics: • New AMPRnet Gateway • New E-mail Gateway Please read this information thoroughly and pass along to any packet users in your local area. New AMPRnet Gateway The AMPRnet is an AMateur Packet Radio network consisting of packet radio BBSs located worldwide. Local networks of BBSs are interconnected to other local networks through gateways. These gateways use IP-in-IP tunnels to connect to each other. AMPRnet IP addresses are allocated from the IP address block of 44.0.0.0/8. Once a BBS or local network of BBSs is connected to AMPRnet, each of the BBSs can reach any other BBS on the AMPRnet, and vice-versa. For example, in the State of Michigan, each county has a local network of one or more BBSs. Each county is connected to all other counties (and to the rest of the world) with AMPRnet connections. Here in California, we can use AMPRnet connections to reach other counties which do not have a radio path to our network. We have just started to reach out to other counties to work on making those connections. There are two primary uses for this connectivity: 1) Messaging: Messages can now be addressed to anyone at any of the AMPRnet BBSs with a simple and standard Internet-style address format: [email protected]. -
LTE-Advanced
Table of Contents INTRODUCTION........................................................................................................ 5 EXPLODING DEMAND ............................................................................................... 8 Smartphones and Tablets ......................................................................................... 8 Application Innovation .............................................................................................. 9 Internet of Things .................................................................................................. 10 Video Streaming .................................................................................................... 10 Cloud Computing ................................................................................................... 11 5G Data Drivers ..................................................................................................... 11 Global Mobile Adoption ........................................................................................... 11 THE PATH TO 5G ..................................................................................................... 15 Expanding Use Cases ............................................................................................. 15 1G to 5G Evolution ................................................................................................. 17 5G Concepts and Architectures ................................................................................ 20 Information-Centric -
Sistemas Informáticos Curso 2005-06 Sistema De Autoconfiguración Para
Sistemas Informáticos Curso 2005-06 Sistema de Autoconfiguración para Redes Ad Hoc Miguel Ángel Tolosa Diosdado Adam Ameziane Dirigido por: Profª. Marta López Fernández Dpto. Sistemas Informáticos y Programación Grupo de Análisis, Seguridad y Sistemas (GASS) Facultad de Informática Universidad Complutense de Madrid AGRADECIMIENTOS: Queremos agradecer la dedicación de la profesora Marta López Fernández, Directora del presente Proyecto de Sistemas Informáticos, y del resto de integrantes del Grupo de Análisis, Seguridad y Sistemas (GASS) del Departamento de Sistemas Informáticos y Programación de la Universidad Complutense de Madrid, y de forma muy especial a Fabio Mesquita Buiati y a Javier García Villalba, Miembro y Director del citado Grupo, respectivamente, por el asesoramiento y las facilidades proporcionadas para el buen término de este Proyecto. 2 Índice RESUMEN ....................................................................................................................... 5 ABSTRACT ..................................................................................................................... 6 PALABRAS CLAVE....................................................................................................... 7 1-INTRODUCCIÓN....................................................................................................... 8 1.1- MOTIVACIÓN ......................................................................................................... 8 1.2 – OBJETIVO ............................................................................................................. -
Mind the Uppercase Letters
Integration of APRS Network with SDI Tomasz Kubik1,2, Wojciech Penar1 1 Wroclaw University of Technology 2 Wroclaw University of Environmental and Life Sciences Abstract. From the point of view of large information systems designers the most important thing is a certain abstraction enabling integration of heterogeneous solutions. Abstraction is associated with the standardization of protocols and interfaces of appropriate services. Behind this façade any device or sensor system may be hidden, even humans recording their measurements. This study presents selected topics and details related to two families of standards developed by OGC: OpenLS and SWE. It also dis- cusses the technical details of a solution built to intercept radio messages broadcast in the APRS network with telemetric information and weather conditions as payload. The basic assumptions and objectives of a prototype system that integrates elements of the APRS network and SWE are given. Keywords: SWE, OpenLS, APRS, SDI, web services 1. Introduction Modern measuring devices are no longer seen as tools for qualitative and quantitative measurements only. They have become parts of highly special- ized solutions, used for data acquisition and post-processing, offering hardware and software interfaces for communication. In the construction of these solutions the latest technologies from various fields are employed, including optics, precision mechanics, satellite and information technolo- gies. Thanks to the Internet and mobile technologies, several architectural and communication barriers caused by the wiring and placement of the sensors have been broken. Only recently the LBS (Location-Based Services) entered the field of IT. These are information services, available from mo- bile devices via mobile networks, giving possibility of utilization of a mobile This work was supported in part by the Polish Ministry of Science and Higher Edu- cation with funds for research for the years 2010-2013.