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Wireless sensor network

Wireless sensor network (WSN), sometimes called wireless sensor and actuator network (WSAN), are spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure etc. and to cooperatively pass their data through the network to a main location. The more modern networks are bi-directional, also enabling control of sensor activity. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and soon.

The WSN is built of “nodes” – from a few to several hundreds or even thousands, where each node is connected to one (or sometimes several) sensors. Each such sensor network node has typically several parts: a radio transceiver with an internal antenna or connection to an external antenna, a micro controller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded from of energy harvesting. A sensor node might vary in size from that of a shoebox down to the size of a grain of dust, although functioning “motos” of genuine microscopic dimensions have yet to be created.

Application

Area monitoring

Area monitoring is a common application of WSNs. In area monitoring, the WSN is deployed over a region where some phenomenon is to be monitored. A military example is the use of sensors detect enemy intrusion; a civilian example is the geo-fencing of gas or oil pipeline.

Health care monitoring

The medical applications can be of two types: wearable and implanted. Wearable devices are used on the body surface of a human or just at close proximity of the user. The implantable medical devices are those that are inserted inside human body. There are many other applications too e.g. body position measurement and location of the person, overall monitoring of ill patients in hospitals and at homes. Body-area networks can collect information about an individual’s health, fitness, and energy expenditure.

Environmental/ Earthsensing

There are many applications in monitoring environmental parameters, examples of which are given below. They share the extra challenges of harsh environments and reduced power supply.

Uniform Resource Locator

A Uniform Resource Locator (URL), commonly informally termed a web address is a reference to a web resource that specifie sits location on a computer network and a mechanism for retrieving is. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. A URL implies the means to access an indicated resource, which is not true of every URI. URLs occur most commonly to reference web pages (http), but are also used for file transfer (ftp), email (mailto), database access (JDBC), and many other applications.

Real-time Transport Protocol

The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and web-based push-to-talk features.

RTP is used in conjunction with the RTP Control Protocol (RTCP). While RTP carries the media streams (e.g., audio and video), RTCP is used to monitor transmission statistics and quality of service (QoS) and aids synchronization of multiple streams. RTP is one of the technical foundations of Voice over IP and in this context is often used in conjunction witha signaling protocol such as the Session Initiation Protocol (SIP) which establishes connections across the network.

Overview

RTP is designed for end-to-end, real-time, transfer of streaming media. The protocol provides facilities for jitter compensation and detection of out of sequence arrival in data, which are common during transmission on an IP network. RTP allows data transfer to multiple destinations through IP multicast. RTP is regarded as the primary standard for audio/video transport in IP networks and is used with an associated profile and payload format.

Real-time multimedia streaming applications require timely delivery of information and often can tolerate some packet lossto achieve this goal. For example, loss of a packet in audio application may result in loss of a fraction of a second of audio data, which can be made unnoticeable with suitable error concealment algorithms. The Transmission Control Protocol (TCP), although standardized for RTP use, is not normally used in RTP applications because TCP favors reliability over timeliness. Instead themajority of the RTP implementations are built on the User Datagram Protocol(UDP). Other transport protocols specifically designed for multimedia sessions are SCTP and DCCP, although, as of 2010, they are not in widespread use.

Protocol components

The RTP specification describes two sub-protocols, RTP and RTCP.

The data transfer protocol, RTP, facilitates the transfer of real-time data. Information provided by this protocol include timestamps, sequence numbers and the payload format which indicates the encoded format of the data.

The control protocol RTCP is used tospecify quality of service (QoS) feedback and synchronization between the media streams. The bandwidth of RTCP traffic compared to RTP is small, typically around 5%.

InternetC ontrol Message Protocol

The Internet Control Message Protocol (ICMP) is one of the main protocols of the Internet protocol suite. It is used by network devices, like routers, to send error messages indicating, for example, that a requested service is not available or that a host or router could not be reached. ICMP can also be used to relay query messages. It is assigned protocol number 1. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications.

Technical details

The Internet Control Message Protocol is part of the Internet Protocol Suite. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations. ICMP errors are directed to the source IP address of the originating packet.

For example, every device (such as an intermediate router) forwarding an IP datagram first decrements the time to live (TTL) field in the IP header by one. If the resulting TTL is 0, the packet is discarded and an ICMP Time To Live exceeded in transit message is sent to the datagram’s source address.

Although ICMP messages are contained within standard IP packets, ICMP messages are usually processed as a special case, distinguished from normal IP processing, rather than processed as a normal sub-protocol of IP. In many cases, it is necessary to inspect the contents of the ICMP message and deliver the appropriate error message to the application responsible for transmission of the IP packet that prompted the sending of the ICMP message.

Many commonly used network utilities are based on ICMP messages. The traceroute command can be implemented by transmitting IP datagrams with specially set IP TTL header fields, and looking for ICMP Time to live exceed in transit an “Destination unreachable” messages generated in response. The related ping utility is implemented using the ICMP “Echo request” and “Echo reply” messages.

From: https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol

Domain

The term domain can refer either to a local subnetwork or to descriptors for sites on the Internet.

Local subnetwork domains

On a local area network (LAN), a domain is a subnetwork made up of a group of clients and servers under the control of one central security database. Within a domain, users authenticate once to centralized server known as a domain controller, rather than repeatedly authenticating to individual servers and services. Individual servers and services accept the user based on the approval of the domain controller.

Internet domains

On the Internet, a domain is part of every network address, including website addresses, email addresses, and addresses for other Internet protocols such as FTP,IRC, and SSH. All devices sharing a common part of an address, or URL, are said to be in the same domain. In the address ‘www.indiana.edu/people/address.shtml', ‘indiana’ is the domain, ‘people’ is a directory in that domain and ‘addres.shtml' is a file in the directory.

To obtain a domain, you must purchase it from a domain registrar. You can choose a registrar from the list of accredited registrars.

From: https://kb.iu.edu/d/aoup

Location-based service

A location-based service (LBS) is a software-level service that uses location data to control features. As such LBS is an information service and has a number of uses in social networking today as information, in entertainment or security, which is accessible with mobile devices through the mobile network and which uses information on the geographical position of the mobile device.

LBS can be used in a variety of contexts, such as health, indoor object search, entertainment, work, personal life, etc.

LBS is critical to many businesses as well as government organizations to drive real insight from data tied to a specific location where activities take place. The spatial patterns that location-related data and services can provide Is one on its most powerful and useful aspect where location is a common denominator in all of these activities and can be leveraged to better understand patterns and relationships.

LBS include service to identify a location of a person or object, such as discovering the nearest banking cash machine(ATM) or the whereabouts of a friend or employee. LBS include parcel tracking and vehicle tracking services. LBS can include mobile commerce when taking the form of coupons or advertising directed at customers based on their current location. They include personalized whether services and even location-based games. They are an example of telecommunication convergence.

Electrical grid

An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of generating stations that produce electrical power, high-voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers.

Power stations may be located near a fuel source, at a dam site, or to take advantage of renewable energy sources, and are often located away from heavily populated areas. They are usually quite large to take advantage of the economies of scale. The electric power which is generated is stepped up to a higher voltage at which it connects to the electric power transmission network.

The bulk power transmission network will move the power long distances, sometimes across international boundaries, until it reaches its wholesale customer (usually the company that owns the local electric power distribution network).

On arrival at a substation, the power will be stepped down from a transmission level voltage to a distribution level voltage. As it exits the substation, it enters the distribution wiring. Finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage(s).

MAC address

A media access control address (MAC address), also called a physical address, of a computer which is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and Wi-Fi. Logically, MAC addresses are used in the media access control protocol sublayer of the OSI reference model.

MAC addresses are most often assigned by the manufacturer of a network interface controller (NIC) and are stored in its hardware, such as the card’s read-only memory or some other firmware mechanism. If assigned by the manufacturer, a MAC address usually encodes the manufacturer’s registered identification number and may be referred to as the burned-in address (BIA). It may also be known as an Ethernet hardware address (EHA), hardware address or physical address. This can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address.

A network node may have multiple NICs and each NIC must have a unique MAC address.

MAC addresses are formed according to the rules of one of three numbering name spaces managed by the IEEE.

Cyclic redundancy check

A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial division of their contents. On retrieval, the calculation is repeated and in the event the check values do not match, corrective action can be taken against data corruption.

CRCs are so called because the check (data verification) value is a redundancy (it expands the message without adding information) and the algorithms is based on cyclic codes. CRCs are popular because they are simple to implement in binary hardware, easy to analyze mathematically, and particularly good at detecting common errors caused by noise in transmission channels. Because the check value has a fixed length, the function that generates it is occasionally used as a hash function.

Introduction

CRCs are based on the theory of cyclic error-correcting codes. The use of systematic cyclic codes, which encode messages by adding a fixed-length check value, for the purpose of error detection in communication networks, was first proposed by W. Wesley Peterson in 1961. Cyclic codes are not only simple to implement but have the benefit particularly well suited for the detection of burst errors, contiguous sequences of erroneous data symbols in messages. This is important because burst errors are common transmission errors in many communication channels, including magnetic and optical storage devices. Typically an n-bit CRC applied to a data block of arbitrary length will detect any single error burst not longer than n bits and will detect a fraction 1-2^-1 of all longer error burst.

HyperText Markup Language (HTML)

HyperText Markup Language, commonly abbreviated as HTML, is the standard markup language used to create web pages. Along with CSS, and JavaScript, HTML is a cornerstone technology used to create web pages, as well as to create user interfaces for mobile and web applications. Web browsers can read HTML files and render them into visible or audible web pages. HTML describes the structure of a website semantically and, before the advent of Cascading Style Sheets (CSS), including cues for the resentation or appearance of the document, making it a markup language, rather than a programming language.