Seminar Report on
Evolution of Wireless Technology
Submitted by
Chinmay Kumar Mishra,
Information Communication Technology,
10IT61B10.
Under the guidedance of
Prof. Indranil Sengupta,
IIT, Kharagpur.
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OUTLINES
1. Introduction ……………………………………………………………….4
2. Mobile Services…………………………………………………………….4
3. Evolution of Wireless Technology…………………………………………5
4. Modes of Communication…………………………………………………6
5. History of Wireless Standards……………………………………………..7
6. Approved and near-term 802.11 Letter Standards……………………….. 7
7. Physical Layer enhancements…………………………………………….. 7
8. Security enhancements ……………………………………………………8
9. Regulatory enhancements………………………………………………….8
10. Types of Wireless Connection……………………………………………..10
11. Mobile devices networks…………………………………………………..11
12. Application of Wireless Network………………………………………….12
13. Wireless in Industry……………………………………………………….13
14. Wireless in Robotics………………………………………………………14
15. Other area of application of WLAN………………………………………15
16. Categories of Wireless Implementation…………………………………..16
17. Future 802.11 Amendments……………………………………………….17
18. Technology………………………………………………………………...18
19. Function of WLANs………………………………………………………19
20. WLAN Configurations…………………………………………………….19
21. Wireless LAN Technology Options……………………………………….20
22. Wireless LAN standards…………………………………………………...21
23. Comparison between Bluetooth and Wi-Fi……………………………….22
24. Conclusion…………………………………………………………………23
25. References…………………………………………………………………24
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List of Figures
Fig-1.
Fig-2
Connection of Bluetooth
Comau SMART robot range: from 6 up to 800 Kg payload
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14
Fig- 3
Teach Pendant for C4G family
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Fig-4
block diagram of DCF
15
Fig-5
technology involve in wireless
18
Fig-6
Block diagram of WLAN
19
Fig-7
Independent WLAN
19
Fig-8
Infrastructure WLANs
20
Fig-9
Microcells and Roaming
20
Fig-10
Wireless standards
21
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INTRODUCTION
It would be hard to imagine a world without wireless applications and services. Around the globe,
mobile services are playing increasingly important roles in many facets of our society. Just a decade ago,
mobile services consisted primarily of basic voice communication. Today, we depend on mobile services not
only for communication, but also for education, entertainment, healthcare, location and m-commerce. Mobile
services have also made significant inroads into developing nations, by improving the quality of life for many
of their citizens.
Wireless computing is a rapidly emerging technology providing users with network connectivity
without being tethered off of a wired network. Wireless local area networks (WLANs), like their wired
counterparts, are being developed to provide high bandwidth to users in a limited geographical area. WLANs
are being studied as an alternative to the high installation and maintenance costs incurred by traditional
additions, deletions, and changes experienced in wired LAN infrastructures. Physical and environmental
necessity is another driving factor in favor of WLANs. Typically, new building architectures are planned with
network connectivity factored into the building requirements. However, users inhabiting existing buildings
may find it infeasible to retrofit existing structures for wired network access. Examples of structures that are
very difficult to wire include concrete buildings, trading floors, manufacturing facilities, warehouses, and
historical buildings. Lastly, the operational environment may not accommodate a wired network, or the
network may be temporary and operational for a very short time, making the installation of a wired network
impractical. Examples where this is true include ad hoc networking needs such as conference registration
centers, campus classrooms, emergency relief centers, and tactical military environments.
Mobile Services
As a society, we are becoming more dependent on mobile services to assist us in life’s everyday
requirements. On a typical day, over 1 billion people worldwide rely on mobile-service offerings to get them
through their daily routine. In the next several paragraphs, we briefly explore various mobile services that
people around the world are using each and every day with growing occurrence.
Mobile Communication—Mobile services are changing the landscape of how we communicate daily;
specifically, the why, when, how often, and in what degree we communicate. Today, mobile communication
can be ubiquitous (anytime, anywhere, anyplace), personal (instant messaging, picture cards, video
messaging) or interactive (push-to-talk [PTT], video telephony, video sharing). Using mobile communication
services has never been easier or more entertaining.
Mobile Enterprise—Mobile enterprise services are at the forefront of early wireless-technology service
adoption. The implementation of mobile enterprise services provides a competitive advantage to corporations
wanting to gain an edge.
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Mobile Entertainment—The days of waiting to get home to indulge your passion for entertainment
are long gone. Like never before, mobile entertainment has given end users the flexibility and freedom to
engage their favorite form of entertainment programming on their terms. Mobile TV (live or cached), videos
and movies (streaming or on demand), music (full tracks), gaming (casual and 3D multiplayer), or social
networking (user-generated or community-developed content) are all available at your fingertips.
Location-Based Services (LBS)—for the enterprise customer, LBS means the efficient tracking of
goods and services. For a consumer, LBS enhance the level of comfort by knowing the location of a child or
elderly parent. For retail shops and restaurants, LBS provide timely directions for a customer who is lost.
Mobile LBS provide end users with location information when and where they need it most.
Mobile Healthcare—Mobile healthcare services are designed to enable a better quality of life 24 hours
a day, seven days a week for outpatient treatment and monitoring procedures. These services allow the capture
of patients’ medical data at the point of care, enabling faster diagnosis and timelier treatments. Mobile
healthcare services provide freedom, mobility and an enhanced sense of wellness for outpatients, and peace of
mind for caregivers.
Mobile Commerce—The old
adage “time is money” has never been truer than in today’s fast-paced
economy. Mobile-commerce services (m-banking, m-payment, e-money, etc.) provide a new level of
convenience and safety for managing money transactions.
The mobile services just reviewed are but a sampling of the many services currently offered
worldwide. As we look into the future, the ways in which we use mobile services will continue to grow, due to
our limitless imagination for improvement in the lives of our fellow man.
Evolution of Wireless Technologies
During the past 10 years, mobile services have evolved from basic voice communication to mobilebroadband multimedia services. The mobile-broadband applications and services commercially available
around the world owe their existence to the evolution of wireless-technology advancements of yesterday and
today. The technology advancements achieved through airlink-performance enhancements—higher
data rates, optimized quality of service (QoS), reduced latency and increased network capacity—
have led to new and enhanced service offerings for mobile operators.
Wireless networking (i.e. the various types of unlicensed 2.4 GHz WiFi devices) is used to meet many needs.
Perhaps the most common use is to connect laptop users who travel from location to location. Another
common use is for mobile networks that connect via satellite. A wireless transmission method is a logical
choice to network a LAN segment that must frequently change locations. The following situations justify the
use of wireless technology:
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To span a distance beyond the capabilities of typical cabling,
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To provide a backup communications link in case of normal network failure,
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To link portable or temporary workstations,
•
To overcome situations where normal cabling is difficult or financially impractical, or
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To remotely connect mobile users or networks.
Modes of Communication:
Wireless communications can be via:
•
radio frequency communication,
•
microwave communication, for example long-range line-of-sight via highly directional antennas, or
short-range communication,
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infrared (IR) short-range communication, for example from consumer IR devices such as remote
controls or via Infrared Data Association (IrDA).
Applications may involve point-to-point communication, point-to-multipoint communication, broadcasting,
cellular networks and other wireless networks.
Cordless
The term "wireless" should not be confused with the term "cordless", which is generally used to refer
to powered electrical or electronic devices that are able to operate from a portable power source (e.g. a battery
pack) without any cable or cord to limit the mobility of the cordless device through a connection to the mains
power supply.
Some cordless devices, such as cordless telephones, are also wireless in the sense that information is
transferred from the cordless telephone to the telephone's base unit via some type of wireless communications
link. This has caused some disparity in the usage of the term "cordless", for example in Digital Enhanced
Cordless Telecommunications.
History of Wireless Standards
1997 the IEEE approved 802.11, which specified the characteristics of devices with a signal rate of 1 and
2 Mb/s.
•
The standard specifies the MAC and the physical layers for transmissions in the 2.4 GHz band.
•
1999, the IEEE ratified a new amendment, called IEEE 802.11b, which works at additional signal
rates of 5.5 and 11 Mb/s.
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•
Hereinafter, to the IEEE 802.11 standards as Wi-Fi (Wireless-Fidelity), certifying device
interoperability.
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1999, the IEEE approved the specifications of 802.11a, which uses the 5 Ghz band. The signal rates
are 6, 9, 12, 18, 24, 36, 48 and 54 Mb/s.
•
In 2003, the IEEE approved 802.11g as a further evolution of the 802.11 standard.
•
802.11g provides the same performance as 802.11a, while working in the 2.4 GHz band. Compatible
with 802.11b devices.
Approved and near-term 802.11 Letter Standards
A number of amendments to the base 802.11 standard have been approved by the IEEE and implemented
by manufacturers since 1997. These can be broadly categorized as follows:
• Faster: Physical Layer enhancements that employ higher order modulation schemes to increase the data
rates deliverable over 802.11. Standards-based Wi-Fi now delivers data rates up to 54 Mbps to Wi-Fi
clients spanning multiple frequency bands.
• Better-performing: Quality of Service enhancements have modified the MAC (Media Access Control—
the signaling scheme between transmitters and receivers) to provide admission control (regulating the
amount of data contending for the wireless medium) and prioritized channel access. The need for a betterperforming MAC has been driven by demanding applications such as voice and video. Better QoS enables
and improves performance of these applications in addition to ordinary data traffic.
• More secure: Security enhancements have been developed to address access control and authentication
(limiting access to the network to authorized users) and data privacy and integrity, driven by the market
requirement for enterprise-level security in wireless LANs.
• Broader applicability: Regulatory enhancements that broaden the applicability of 802.11 to other
frequencies such as 4.9 GHz in Japan and additional regulatory domains. These open up new markets to
Wi-Fi technology including large parts of Europe and Asia. These enhancements have accelerated the
volume of Wi-Fi shipments by making it the first truly global data radio standard. A bit more detail on the
evolution of 802.11 follows, including discussion of expected nearterm enhancements.
Physical Layer enhancements
802.11a and 802.11b were approved in 1999. 802.11a, which defines a physical layer for operation in the 5
GHz unlicensed bands, uses OFDM modulation and provides raw data rates up to 54 Mbps. 802.11b defines
CCK modulation to deliver raw data rates up to 11 Mbps in the 2.4 GHz band. 802.11g, a backwardscompatible extension to the 802.11b standard in the 2.4 GHz band, was approved in 2003. It allows data rates
up to 54 Mbps through use of OFDM or CCK modulation. While 802.11g and 802.11a nominally offer higher
data rates, it is important to recognize that these higher data rates will require much higher cell densities to
realize in practice.For example, typical access points can provide 54 Mbps data rates only up to tens of feet
whereas they can extend 11 Mbps data rates up to hundreds of feet. This is because these higher rates require
higher levels of signal-to-noise ratio (SNR) at the receiver.
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Security enhancements
802.11i, approved in 2004, defines strong authentication and access control mechanisms leveraging RADIUS
(the most common form of subscriber directory) EAP, the Extensible Authentication Protocol, and 802.1 xs,
an IEEE standard for securing LANs. The standard also defines 802.11 key management using 802.1x/EAP
and support for stronger encryption and data confidentiality using TKIP and AES as well as stronger message
integrity checking. 802.11i will make 802.11 wireless networks more secure and is expected to lead to broader
adoption in enterprise settings. For those networks that do not have a RADIUS server or AAA backend
802.11i also defines an authentication and key management system based on a Pre-Shared Key (PSK).
WPA (Wi-Fi Protected Access) was adopted by the Wi-Fi Alliance in 2003. While not an IEEE standard, it is
an interim proposal based on an early draft version of the 802.11i standard that was adopted because of the
urgency of security needs. Designed to be a software-only upgrade to equipment already deployed, WPA
includes TKIP and 802.1x authentication and dynamic key management. Vendors can receive WPA
certification for 802.1x/EAP implementations, called WPA-Enterprise, or for PSK implementations, called
WPA-Personal.
WPA2 (Wi-Fi Protected Access version2) is a certification regime adopted by the Wi-Fi Alliance in 2006. It
consists of all mandatory requirements from the 802.11i amendment and does not introduce any new
functionality. Like it’s earlier sibling, there is both WPA2- Enterprise certification for 802.1x/EAP
implementations and WPA2-Personal certification for PSK authentication.
Regulatory enhancements
802.11d (approved in 2001) and 802.11h (approved in 2003) extend the physical and MAC layer to allow
802.11 to operate in regulatory domains of other countries. Because regulatory requirements regarding the use
of the 5 GHz band vary from country to country, the ITU (International Telecommunications Union)
recommended a harmonized set of rules to allow unlicensed transmitters in this band to coexist with primaryuse devices such as military radar systems in Europe. 802.11h defines mechanisms such as Transmit Power
Control (TPC) and Dynamic Frequency Selection (DFS) to allow for licensed-unlicensed coexistence in the 5
GHz band. These rules allow unlicensed transmitters to employ more sophisticated versions of “listen-beforetalk” to adjust the transmit power and intelligently select the operating channel so as to more efficiently use
the available spectrum and to avoid causing harmful interference.
802.11j (approved in 2004) defined regulatory and protocol extensions to allow for operation in the 4.9 GHz
and 5GHz bands in Japan.
QoS enhancements 802.11e (approved in 2005) provides quality of service enhancements to the base
standard. The first implementations have centered around the multiple queue capability defined in the
amendment. This enables time-sensitive traffic (e.g., voice) to gain access to the medium more quickly than
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best-effort data traffic. This will lead to greatly improved performance for applications such as video,
multimedia streaming and voice.
1.Photophone:-The world's first wireless telephone conversation occurred in 1880, when Alexander
Graham Bell and Charles Sumner Tainter invented and patented the photophone, a telephone that conducted
audio conversations wirelessly over modulated light beams (which are narrow projections of electromagnetic
waves). In that distant era when utilities did not yet exist to provide electricity, and lasers had not even been
conceived of in science fiction, there were no practical applications for their invention, which was highly
limited by the availability of both sunlight and good weather. Similar to free space optical communication, the
photophone also required a clear line of sight between its transmitter and its receiver. It would be several
decades before the photophone's principles found their first practical applications in military communications
and later in fiber-optic communications.
2.
Early wireless work:- David E. Hughes,
eight years before Hertz's experiments, transmitted radio
signals over a few hundred yards by means of a clockwork keyed transmitter. As this was before Maxwell's
work was understood, Hughes' contemporaries dismissed his achievement as mere "Induction". In 1885, T. A.
Edison used a vibrator magnet for induction transmission. In 1888, Edison deployed a system of signaling on
the Lehigh Valley Railroad. In 1891, Edison obtained the wireless patent for this method using inductance.
In the history of wireless technology, the demonstration of the theory of electromagnetic waves by
Heinrich Hertz in 1888 was important.[2][3] The theory of electromagnetic waves was predicted from the
research of James Clerk Maxwell and Michael Faraday. Hertz demonstrated that electromagnetic waves could
be transmitted and caused to travel through space at straight lines and that they were able to be received by an
experimental apparatus. The experiments were not followed up by Hertz. Jagadish Chandra Bose around this
time developed an early wireless detection device and helped increase the knowledge of millimeter length
electromagnetic waves. Practical applications of wireless radio communication and radio remote control
technology were implemented by later inventors, such as Nikola Tesla.
3.
Radio:-
The term "wireless" came into public use to refer to a radio receiver or transceiver (a dual
purpose receiver and transmitter device), establishing its usage in the field of wireless telegraphy early on;
now the term is used to describe modern wireless connections such as in cellular networks and wireless
broadband Internet. It is also used in a general sense to refer to any type of operation that is implemented
without the use of wires, such as "wireless remote control" or "wireless energy transfer", regardless of the
specific technology (e.g. radio, infrared, ultrasonic) used. Guglielmo Marconi and Karl Ferdinand Braun were
awarded the 1909 Nobel Prize for Physics for their contribution to wireless telegraphy.
4. Electromagnetic
spectrum:- Light, colors, AM and FM radio, and electronic devices make use of
the electromagnetic spectrum. The frequencies of the radio spectrum that are available for use for
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communication are treated as a public resource and are regulated by national organizations such as the Federal
Communications Commission in the USA, or Ofcom in the United Kingdom. This determines which
frequency ranges can be used for what purpose and by whom. In the absence of such control or alternative
arrangements such as a privatized electromagnetic spectrum, chaos might result if, for example, airlines didn't
have specific frequencies to work under and an amateur radio operator were interfering with the pilot's ability
to land an aircraft. Wireless communication spans the spectrum from 9 kHz to 300 GHz.
Types of wireless connections
Wireless PAN
Wireless Personal Area Networks (WPANs) interconnect devices within a relatively small area that is
generally within a person's reach. For example, both Bluetooth radio and invisible Infrared light provides a
WPAN for interconnecting a headset to a laptop. ZigBee also supports WPAN applications. Wi-Fi PANs are
becoming commonplace (2010) as equipment designers start to integrate Wi-Fi into a variety of consumer
electronic devices. Intel "My Wi-Fi" and Windows 7 "virtual Wi-Fi" capabilities have made Wi-Fi PANs
simpler and easier to set up and configure.
Wireless LAN
A wireless local area network (WLAN) links two or more devices over a short distance using a wireless
distribution method, usually providing a connection through an access point for Internet access. The use of
spread-spectrum or OFDM technologies may allow users to move around within a local coverage area, and
still remain connected to the network.
Products using the IEEE 802.11 WLAN standards are marketed under the Wi-Fi brand name. Fixed wireless
technology implements point-to-point links between computers or networks at two distant locations, often
using dedicated microwave or modulated laser light beams over line of sight paths. It is often used in cities to
connect networks in two or more buildings without installing a wired link.
Wireless mesh network
A wireless mesh network is a wireless network made up of radio nodes organized in a mesh topology. Each
node forwards messages on behalf of the other nodes. Mesh networks can "self heal", automatically re-routing
around a node that has lost power.
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Wireless MAN
Wireless Metropolitan Area Networks are a type of wireless network that connects several wireless LANs.
•
WiMAX is a type of Wireless MAN and is described by the IEEE 802.16 standard.
Wireless WAN
Wireless wide area networks are wireless networks that typically cover large areas, such as between
neighboring towns and cities, or city and suburb. These networks can be used to connect branch offices of
business or as a public internet access system. The wireless connections between access points are usually
point to point microwave links using parabolic dishes on the 2.4 GHz band, rather than unidirectional
antennas used with smaller networks. A typical system contains base station gateways, access points and
wireless bridging relays. Other configurations are mesh systems where each access point acts as a relay also.
When combined with renewable energy systems such as photo-voltaic solar panels or wind systems they can
be stand alone systems.
Mobile devices networks
With the development of smart phones, cellular telephone networks routinely carry data in addition to
telephone conversations:
1.
Global System for Mobile Communications (GSM): The GSM network is divided
into three major systems: the switching system, the base station system, and the operation and support
system. The cell phone connects to the base system station which then connects to the operation and
support station; it then connects to the switching station where the call is transferred to where it needs
to go. GSM is the most common standard and is used for a majority of cell phones.
2.
Personal Communications Service (PCS):
PCS is a radio band that can be used by
mobile phones in North America and South Asia. Sprint happened to be the first service to set up a
PCS.
3.
D-AMPS: Digital Advanced Mobile Phone Service, an upgraded version of AMPS, is being phased
out due to advancement in technology. The newer GSM networks are replacing the older system.
Applications of wireless technology
1. Security systems:-Wireless technology may supplement or replace hard wired implementations in security
systems for homes or office buildings.
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2. Mobile telephones:-One of the best-known examples of wireless technology is the mobile phone, also
known as a cellular phone, with more than 4.6 billion mobile cellular subscriptions worldwide as of the end of
2010. These wireless phones use radio waves to enable their users to make phone calls from many locations
worldwide. They can be used within range of the mobile telephone site used to house the equipment required
to transmit and receive the radio signals from these instruments.
3. Wireless data communications:-Wireless data communications are an essential component of mobile
computing. The various available technologies differ in local availability, coverage range and performance,
and in some circumstances, users must be able to employ multiple connection types and switch between them.
To simplify the experience for the user, connection manager software can be used, or a mobile VPN deployed
to handle the multiple connections as a secure, single virtual network. Supporting technologies include:
1. Wi-Fi is a wireless local area network that enables portable computing devices to connect easily to
the Internet. Standardized as IEEE 802.11 a, b, g, n, Wi-Fi approaches speeds of some types of wired
Ethernet. Wi-Fi has become the de facto standard for access in private homes, within offices, and at
public hotspots. Some businesses charge customers a monthly fee for service, while others have
begun offering it for free in an effort to increase the sales of their goods.
2. Cellular data service offers effective coverage within a range of 10-15 miles from the nearest cell
site. Speeds have increased as technologies have evolved, from earlier technologies such as GSM,
CDMA and GPRS, to 3G networks such as W-CDMA, EDGE or CDMA2000.
3. Mobile Satellite Communications may be used where other wireless connections are unavailable,
such as in largely rural areas or remote locations. Satellite communications are especially important
for transportation, aviation, maritime and military use. Wireless energy transfer is a process whereby
electrical energy is transmitted from a power source to an electrical load that does not have a built-in
power source, without the use of interconnecting wires.
4. Computer interface devices:-Answering the call of customers frustrated with cord clutter, many
manufactures of computer peripherals turned to wireless technology to satisfy their consumer base.
Originally these units used bulky, highly limited transceivers to mediate between a computer and a
keyboard and mouse, however more recent generations have used small, high quality devices, some
even incorporating Bluetooth. These systems have become so ubiquitous that some users have begun
complaining about a lack of wired peripherals.
5. Bluetooth:-A connection between two or more portable devices without the need for cables or
connectors the transceiver transmits and receives in a previously unused frequency band of 2.45 GHz
that is available globally. The maximum range is 10 meters. Data can be exchanged at a rate of 1
megabit per second (up to 2 Mbps in the second generation of the technology). A frequency hop
scheme allows devices to communicate even in areas with a great deal of electromagnetic
interference. Built-in encryption and verification is provided.
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(Fig-1.connection of Bluetooth)
Wireless in the industry
When considering the introduction of wireless technology into manufacturing plants, different aspects
must be considered:
1. Costs. The first reason justifying wireless deployment is always cost saving due to wire replacement; the
industrial case is particularly critical due to the high costs of industrial wiring.
2. Resiliency and Safety: - The impact of a link failure event over system safety must be minimized: wireless
is vulnerable to noise, temporary interferences, fading. A receiver can be “jammed” quite easily. Usually,
these are the first objections to wireless: anyway there are several possible solutions preventing such problems
and, don’t forget it, wires can be cut (and hard to repair) and wired devices (switches, hubs, repeaters) break!
3. Priority: - Safety requirements involve the use of a protocol which is reliable and offers real-time
guarantees for the most important signals. Not all the protocols are suitable for this. Consider that if, on one
hand, you can ensure safety by a simple approach which interrupts processes whenever messages get lost, on
the other hand you cannot afford too many interruptions if you do not want to cut down the efficiency of your
process.
4. Security: - Another threat concerns wireless vulnerability. Anyway this can be considered a thing of the
past several solutions exist to improve security and privacy of wireless transmissions.
5. Mobility: - Wireless means mobility. Freedom from wires brings several benefits: you can move around
your plant without disrupting connectivity; in case of frequent reconfiguration of your plant involving
assembly lines, you do not have to deal with cable bonds. In most cases, an industrial application requires
more a nomadic rather than a true mobile solution: this means that you work in quasi-static scenarios on
which wireless is particularly effective.
6. Scalability:- Intuitively, a wireless solution is more efficient if it allows for an increase of the number of
users connected to the same device (overcoming the paradigm of a point-to-point connection), number of
active networks, capability to automatic configuration. This will be further discussed in next section.
7. Protocols Inter-operation:- Several different industrial communication standards compete and cannot
inter-work each other. A wireless protocol can behave as a bridging protocol among them.
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8. Fabric-to-Office Integration:- A wireless protocol can efficiently transport also office-related and
internet-oriented traffic. This would allow to carrying on the evolution started by industrial Ethernet,
optimizing network maintenance costs and always-on connection to the office. The integration with the office
(the so called “global networking”) enables, in perspective, added valued industrial management (automated
asset management, supply chain management, customer relationship management).
9. Dynamic Chain Configuration:- On the other hand, fabric-to-office integration enables to draw an
improved production environment, flexible and dynamically re-configurable according to highly differentiated
customer requests recalling data (for instance orders) stored on other systems.
Wireless in robotics:
The above considerations are especially true for robotics. This scenario introduces however some further
ingredients, with relative requirements and constraints. More in details, industrial solutions using robots, as
those traditionally included in Comau’s portfolio, foresee a working set, including a robot (see Fig. 2.), and a
control unit with its Teach Pendant (Fig. 3), the hand-held device which allows remote control of the robot
and simplifies monitoring (it collects signals and provides a smart display of the information).
(Fig. 2 – Comau SMART robot range: from 6 up to 800 Kg payload)
A careful analysis of the characteristics (timing requirements, resiliency, semantics, etc.) of the signals being
exchanged by the units must be the starting point for the design of any wireless solution. This is a typical
point-to-point communication scenario, where expensive cabling forces each Teach Pendant (TP) to be
dedicated to a single robot. Wireless connectivity allows to overcoming this paradigm: a single TP can
monitor and even coordinate several robot units at the same. This implies the use of a multiple access wireless
technology: if the wireless medium can be shared among multiple users, multiple devices can contemporarily
talk to each other.
Fig. 3 - Teach Pendant for C4G family
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Multiple access wireless means that a single operator can connect several units at the same time, but also that
several operators can monitor and collect alarms from the same unit. Furthermore, several units can coordinate
at run time; this implements a general purpose scenario which can be called “multipoint wireless” (may mean
machine-to-machine, manto-machine or machine-to-man data communication). Moreover, with a multipleaccess capability, additional data, such as video sequences or sensor measures, could be contemporarily
collected. This would significantly improve early fault discovery and diagnosis: monitoring could get more
efficient and even a large plant could be potentially monitored by a single location. This would be a further
improvement (in terms of flexibility) but would require also a large capacity channel (that is a broadband
wireless technology) and a flexible channel able to differentiate among different data profiles (that is a
differentiated or prioritized technology).
Other area of applications for Wireless LANs
1. Hospitals
2. Consulting or accounting audit teams.
3. In dynamic environments minimize the overhead of moves, ads, and changes with wireless
LANs.
4. Used on Training sites at corporations and students at universities.
5. Easy setup in older buildings
6. Retail store IS managers use wireless networks to simplify frequent network reconfiguration.
7. Warehouse workers use wireless LANs to exchange information with central databases and
increase their productivity.
8. To backup for mission-critical applications running on wired networks.
9. Real-time customer information input and retrieval.
Distribution Coordinating Function (DCF)
Distribution Coordinating Function (DCF) is based on carrier sense multiple accesses with collision avoidance
(CSMA/CA). Receivers send an ACK if they successfully receive a packet, otherwise the transmitter resends
(Fig-4 block diagram of DCF)
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Categories of wireless implementations
1.
Radio communication system
2.
Broadcasting
3.
Amateur radio
4.
Land Mobile Radio or Professional Mobile Radio: TETRA, P25, OpenSky, EDACS, DMR, dPMR
5.
Communication radio
6.
Cordless telephony:DECT (Digital Enhanced Cordless Telecommunications)
7.
Cellular networks: 0G, 1G, 2G, 3G, Beyond 3G (4G), Future wireless
8.
List of emerging technologies
9.
Short-range point-to-point communication : Wireless microphones, Remote controls, IrDA, RFID
(Radio Frequency Identification), TransferJet, Wireless USB, DSRC (Dedicated Short Range
Communications), EnOcean, Near Field Communication
10. Wireless sensor networks: ZigBee, EnOcean; Personal area networks, Bluetooth, TransferJet, Ultra-
wideband (UWB from WiMedia Alliance).
11. Wireless networks: Wireless LAN (WLAN), (IEEE 802.11 branded as Wi-Fi and HiperLAN),
Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA) (LMDS,
WiMAX, AIDAAS and HiperMAN).
Future 802.11 Amendments
The following amendments are expected to be codified over the next few years, with 802.11k expected in
2007.
802.11k
802.11k is focused on standardizing the radio measurements that will allow uniform measurement of radio
information across different manufacturer platforms. By having standardized, repeatable measurements,
system designers can utilize radio environment information to make better decisions as to frequency use,
transmit power levels, etc. This will lead to 802.11 networks that are easier to monitor and manage and that
can make more efficient use of the available spectrum.
802.11n
The 802.11n Task Group is focusing on creating a standard to further increase the net throughput of wireless
networks. The goal is to achieve greater than 150 Mbps data rate over an 802.11 communications channel.
Both physical and MAC layer changes are being considered, but backward compatibility is required to both
802.11a and 802.11g. This new standard will enable 802.11 to meet the growing need for more data-intensive
applications as well as aggregating traffic from multiple access points or cells together. One key aspect of
802.11n is maximum-ratio combining, which allows for improvement of the link budget due to efficient signal
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processing of signals received on multiple antennas. We note that it is currently unclear how significant the
gains of MIMO technology will be in outdoor metro-scale environments.
802.11r
The 802.11r Task Group is working on reducing the handoff latency when client devices transition between
access points or cells in an Extended Service Set (ESS), i.e., a collection of access points in the same network.
Faster handoffs will be critical to meeting the real time requirements of delay-sensitive applications such as
voice, especially in mobile settings where client devices can be expected to roam frequently. This amendment,
when supported on client devices, will facilitate the deployment of SIP-based Voice over Wi-Fi (VoWi-Fi)
portable phones.
802.11s
The 802.11s Task Group is working on an infrastructure mesh amendment to allow 802.11 access points or
cells from multiple manufacturers to self-configure into multi-hop wireless topologies. We expect that a mesh
standard would enlarge the range of markets and applications for the 802.11 standard. Example usage
scenarios for mesh networks include interconnectivity for devices in the digital home, unwired campuses, and
community area networks or hot zones. The standard is expected to be designed to be extensible by
manufacturers to enable diverse usage scenarios with differing functional requirements. For example, some
applications may require quick ad-hoc setup and teardown of a mesh while others require large scale and
maximum throughput.
802.11v
The 802.11v Task Group is working on a follow-on amendment to 802.11k for network management, whereas
11k is just for measurement. This will allow more detailed and specific management of clients. The result is
that infrastructure systems can have greatly increased control of the clients that attach to it, and overall system
capacity and performance can improve.
802.11y
The 802.11y Task Group is working on an amendment to enable operation in the USA 3650-3700 MHz
frequency band. Recent rulings by the US Federal Communications Commission have formalized that this
band will operate under listen-before-talk rules, which the 802.11 MAC follows. As such, 802.11y is defining
the protocol for 802.11 operations in this frequency band. Since the scope of this amendment is smaller, it is
expected to finish more quickly, and should be done in the first half of 2008.
Standards Evolution of 802.11
Over the last several years the successive enhancements to the MAC and Physical Layer have dramatically
increased the system capacity of 802.11 networks. Early work, focused on higher order modulation schemes,
has delivered peak raw data rates up to 54 Mbps over a 20 Hz channel. The currently active 802.11n Task
Group is looking into ways to further increase maximum data rates to over 150 Mbps using a variety of
approaches including channel bonding and MIMO (Multiple Input, Multiple Output) technology. The chart
below illustrates the evolution of the standard’s ability to support higher data rates.
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Technology
(Fig-5 technology involve in wireless)
Function of WLANs:Wireless LANs use electromagnetic airwaves (radio and infrared) to communicate information from
one point to another without relying on any physical connection. Radio waves are often referred to as radio
carriers. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted
at the receiving end. A transmitter/receiver (transceiver) device, called an access point, connects to the wired
network from a fixed location using standard Ethernet cable. End users access the WLAN through Wireless
LAN adapters. WLAN adapters provide an interface between the client network operating system (NOS) and
the airwaves (via an antenna). The nature of the wireless connection is transparent to the NOS.
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(Fig-6 Block diagram of WLAN)
WLAN Configurations
• Independent WLANs
Connects a set of PCs with wireless adapters. Any time two or more wireless adapters are within range of
each other, they can set up an independent network. Access points can extend the range of independent
WLANs by acting as a repeater.
(Fig-7 Independent WLAN)
Infrastructure WLANs
Multiple access points link the WLAN to the wired network to efficiently share network resources. Mediate
wireless network traffic in the immediate neighborhood. Multiple access points can provide wireless coverage
for an entire building or campus.
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(Fig-8 Infrastructure WLANs)
• Microcells and Roaming
WLANs use cells, called microcells, similar to the cellular telephone system to extend the range of wireless
connectivity. Individual microcells overlap to allow continuous communication within wired network. They
handle low-power signals and “hand off” users as they roam through a given geographic area.
(Fig-9 Microcells and Roaming)
Wireless LAN Technology Options
1.
Narrowband Technology
A narrowband radio system transmits and receives user information on a specific radio Frequency.
Undesirable crosstalk between communications channels is avoided by carefully coordinating
different users on different channel frequencies.
2.
Spread Spectrum
Its a wideband radio frequency technique developed by the military for use in reliable, secure, missioncritical communications systems. Spread-spectrum is designed to trade off andwidth efficiency for
reliability, integrity, and security.
3.
Frequency-Hopping Spread Spectrum
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It uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver.
FHSS appears to be short duration impulse noise.
4.
Direct-Sequence Spread Spectrum
DSSS generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip
(or chipping code). DSSS appears as low-power wideband noise and is rejected (ignored) by most
narrowband receivers.
5.
Infrared Technology
Infrared (IR) systems use very high frequencies, just below visible lighting the
electromagnetic
spectrum, to carry data. High performance directed IR is impractical for mobile users. Diffuse (or
reflective) IR WLAN systems do not require line-of sight, but cells are limited to individual rooms.
Wireless LAN standards – 802.11
802.11 is a member of the IEEE 802 family, including several standards. The standards define transmission
protocols and bandwidth
( Fig-10 Wireless standerds)
b – Available several years, 11Mbit/s, 2.4GHz, not standardized 22Mbits in 2.4GHz band of several vendors
(sometimes called b+, channel bundling).
g – defined 2003, 108Mbits, 2.4GHz, OFDM (orthogonal frequency division multiplexing) most of the
hardware sold at the moment confirms to this standard backward compatible to “b”, but then more overhead
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compared to “clean” g standard networks (preamble an initialization sequence must be handled within b
standard).
a – 54Mbit/s standard for the 5GHz band, 12 non-overlapping channels, OFDM, restricted output power,
Introduction of transmit power control (TPC) and dynamic frequency selection (DFC), DFS should reduce the
transmission power so it is sufficient for a given connection but does not spread farther than needed, it checks
if the used frequency is free and sufficient,
if not tries to switch over to another frequency with DFC band is reserved for WLAN only, range is more
restricted than with 802.11b, bandwidth is increased up to 108Mbit/s More standards defining several other
aspects of WLANs.
c – Wireless bridging
d – World mode (combined definitions for different countries)
e – Quality of service (QoS on layer 2), packet priorization for real time multimedia and Voice over IP.
f – General definition of roaming between access points (of different vendors)
i – Authentication and encryption
k – Better measurement of WLAN parameters for increase of signal quality, dense networks
and location based services (LBS)
m – Summarization of extensions to the protocol
n – Extension of bandwidth up to 108-320Mbit/s
Comparison between Bluetooth and Wi-Fi
Bluetooth
Lower cost
Wi-Fi
Higher cost
Uses less power
Uses more power
Data Rate=1Mbps
Data Rate=11 Mbps
Typical distance=100 feet
Typical distance=300 feet
Use to replace cable
Use to access Ethernet
Without cables or wires to
become WLAN
(Wireless Local Area Network)
PAN (Personal Area Network)
Ad-hoc network (links notebooks with cell
phone or PDA)
Excellent for corporate
infrastructure, small
business/home business
LAN-in-a-box.
Extension or replacement of a
wired LAN infrastructure
Localized voice connectivity
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Conclusion
No doubt wireless network is an amazing wireless technology which has totally changes the means of
communication. There is no business, industry, project which can be progressed without the needs of wireless
networks. Now a wireless network has become the significant option of any business because of its salient
features like speed, security, mobility and WiFi hotspot. Voice application like VOIP (Voice over Internet
Protocol) can be only possible because of wireless network. Now wireless network has become the essential
point of any network to make their customer more satisfied.
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