WLANs Technology

There are three main ways by which WLANs transmit information : microwave, spread spectrum and infrared.

 

Microwave Transmission

Motorola's WLAN product (ALTAIR) transmits data by using low powered microwave radio signals. It operates at the 18GHz frequency band.

 

Spread Spectrum Transmission

With this transmission technology, there are two methods used by wireless LAN products : frequency hopping and direct sequence modulation.

• Frequency Hopping
  The signal jumps from one frequency to another within a given frequency range. The transmitter device "listens" to a channel, if it detects an idle time (i.e. no signal is transmitted), it transmits the data using the full channel bandwidth. If the channel is full, it "hops" to another channel and repeats the process. The transmitter and the receiver "jump" in the same manner.
• Direct Sequence Modulation
  This method uses a wide frequency band together with Code Division Multiple Access (CDMA). Signals from different units are transmitted at a given frequency range. The power levels of these signals are very low (just above background noise). A code is transmitted with each signal so that the receiver can identify the appropriate signal transmitted by the sender unit.
  The frequency at which such signals are transmitted is called the ISM (industrial, scientific and medical) band. This frequency band is reserved for ISM devices. The ISM band has three frequency ranges : 902-928, 2400-2483.5 and 5725-5850 MHz. An exception to this is Motorola's ALTAIR which operates at 18GHz.
  Spread spectrum transmission technology is used by many wireless LAN manufacturers such as NCR for waveLAN product and SpectraLink for the 2000 PCS.

 

Infrared Transmission

This method uses infrared light to carry information. There are three types of infrared transmission : diffused, directed and directed point-to-point.

• Diffused
  The infrared light transmitted by the sender unit fills the area (e.g. office). Therefore the receiver unit located anywhere in that area can receive the signal.
• Directed
  The infrared light is focused before transmitting the signal. This method increases the transmission speed.
• Directed point-to-point
  Directed point-to-point infrared transmission provides the highest transmission speed. Here the receiver is aligned with the sender unit. The infrared light is then transmitted directly to the receiver.

The light source used in infrared transmission depends on the environmemt. Light emitting diode (LED) is used in indoor areas, while lasers are used in outdoor areas.
Infrared radiation (IR) has major biological effects. It greatly affects the eyes and skin. Microwave signals are also dangerous to health. But with proper design of systems, these effects are reduced considerably.

Wireless Technology

Types of Wireless Technology

Eighteen major types of wireless technologies exist, containing a large number of subset technologies that range from ATM-protocol based (which sells at approximately $200,000 per data link, to wireless local-area network (WLAN, which sells at less than $500,000 per data link). Frequencies of the different technologies travel between several hundred feet (wireless LAN) and 25 miles (MMDS).

The process by which radio waves are propagated through the air, the amount of data carried, immunity to interference from internal and external sources, and a host of other characteristics varies from technology to technology.

Wireless technologies are differentiated by the following:

• Protocol - ATM or IP
• Connection type - Point-to-Point (P2P) or multipoint (P2MP) connections
• Spectrum - Licensed or unlicensed

Different Types of Wireless Technologies

Broadband	Narrowband
WAN	WAN and WLAN
Licensed	Unlicensed
Digital	Analog
Line-of-site	Non-line-of-site
Simplex	Half-/full-Duplex
Point-to-point	Multipoint

Wireless Technologies

Different Types of Wireless Technologies

Broadband	Narrowband
WAN	WAN and WLAN
Licensed	Unlicensed
Digital	Analog
Line-of-site	Non-line-of-site
Simplex	Half-/full-Duplex
Point-to-point	Multipoint

Wireless technologies are differentiated by the following:

• Protocol - ATM or IP
• Connection type - Point-to-Point (P2P) or multipoint (P2MP) connections
• Spectrum - Licensed or unlicensed

Wireless communication is among technology’s biggest contributions to mankind. Wireless communication involves the transmission of information over a distance without help of wires, cables or any other forms of electrical conductors. The transmitted distance can be anywhere between a few meters (for example, a television’s remote control) and thousands of kilometres (for example, radio communication).

Some of the devices used for wireless communication are cordless telephones, mobiles, GPS units, wireless computer parts, and satellite television.

Advantages

Wireless communication has the following advantages:

i.      Communication has enhanced to convey the information quickly to the consumers. 

ii.        Working professionals can work and access Internet anywhere and anytime without carrying cables or wires wherever they go. This also helps to complete the work anywhere on time and improves the productivity. 

iii.       Doctors, workers and other professionals working in remote areas can be in touch with medical centres through wireless communication. 

iv.       Urgent situation can be alerted through wireless communication. The affected regions can be provided help and support with the help of these alerts through wireless communication. 

v.         Wireless networks are cheaper to install and maintain.

Disadvantages

The growth of wireless network has enabled us to use personal devices anywhere and anytime. This has helped mankind to improve in every field of life but this has led many threats as well.

Wireless network has led to many security threats to mankind. It is very easy for the hackers to grab the wireless signals that are spread in the air. It is very important to secure the wireless network so that the information cannot be exploited by the unauthorized users. This also increases the risk to lose information. Strong security protocols must be created to secure the wireless signals like WPA and WPA2. Another way to secure the wireless network is to have wireless intrusion prevention system.  

Types of wireless communication

The different types of wireless communication technologies include:

i. Infrared (IR) wireless communication:

IR wireless communication communicates data or information in devices or systems through infrared (IR) radiation.  Infrared is electromagnetic energy at a wavelength that is longer than that of red light.

Working:

IR wireless is used for short and medium-range communications and security control.  For IR communication to work, the systems mostly operate in line-of-sight mode which means that there must be no obstruction between the transmitter (source) and receiver (destination).  

Infrared is used in television remote controls and security systems.

In the electromagnetic spectrum, infrared radiation lies between microwaves and visible light, therefore, they can be used as a source of communication.

A photo LED transmitter and a photodiode receptor are required for successful IR communication. The LED transmitter transmits the infrared signal in the form of non-visible light, which is captured and retrieved as information by the photo receptor. In this way, the information between the source and the target is transferred.

The source and/or destination can be laptops, mobile phones, televisions, security systems and any other device that supports wireless communication.

Types of Wireless Technologies

It wasn't so long ago that "wireless technology" invoked thoughts of brick-like cellular phones. Today, the term "wireless" refers to a variety of technologies and devices, from smartphones to computers and printers to headphones and speakers, connecting with one or more methods. Current wireless phones, for example, may include 3G and 4G cellular radios, Wi-Fi and Bluetooth technologies. As these technologies advance, investing in the latest wireless equipment, such as a 4G phone or 802.11ac router, could offer you serious speed improvements.

 

• Wi-Fi 

Primarily associated with computer networking, Wi-Fi uses the IEEE 802.11 specification to create a wireless local-area network that may be secure, such as an office network, or public, such as a coffee shop. Usually a Wi-Fi network consists of a wired connection to the Internet, leading to a wireless router that transmits and receives data from individual devices, connecting them not only to the outside world but also to each other.

 

• Cellular

Most often associated with wireless phones, a cellular network uses connected transmitters, or cells, that enable the user to move about while remaining in contact with the network. Cells transmit at low power levels so as not to interfere with each other and may be spaced far apart in rural areas or close together in cities. Cellular networks rarely offer complete coverage, and due to a number of factors, you may have experienced "dead zones" with no coverage at all.

 

• Bluetooth 

While both Wi-Fi and cellular networks enable connections to anywhere in the world, Bluetooth is much more local, with the stated purpose of "replacing the cables connecting devices," according to the official Bluetooth website. That's precisely what Bluetooth does; it connects iPods to car stereos, wireless keyboards and mice to laptops or cell phones to the ubiquitous hands-free earpieces.

 

• WiMAX

While over-the-air data is fast becoming the realm of cellular providers, dedicated wireless broadband systems also exist, offering fast Web surfing without connecting to cable or DSL. One well-known example of wireless broadband is WiMAX, offered by providers such as Clear or Skyriver. Although WiMAX can potentially deliver data rates of more than 30 megabits per second, providers offer average data rates of 6 Mbps and often deliver less, making the service significantly slower than hard-wired broadband.

Wireless Technology

Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.

The most common wireless technologies use radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice,keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.

Somewhat less common methods of achieving wireless communications include the use of otherelectromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.

Wireless Technology

Wireless technology explained with examples

Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or all of the communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.

The wireless method of communication uses low-powered radio waves to transmit data between devices. High powered transmission sources usually require government licenses to broadcast on a specific wavelength. This platform has historically carried voice and has grown into a large industry, carrying many thousands of broadcasts around the world. Radio waves are now increasingly being used by unregulated computer users.

Humans communicate in order to share knowledge and experiences. Common forms of human communication include sign language, speaking, writing, gestures, and broadcasting. Communication can be interactive, transactive, intentional, or unintentional; it can also be verbal or nonverbal. In addition, communication can be intrapersonal or interpersonal.

We owe much to the Romans that in the field of communication it did not end with the Latin root communicare. They devised what might be described as the first real mail, or postal system, in order to centralize control of the empire from Rome. This allowed Rome to gather knowledge about events in its many widespread provinces.

The first wireless transmitters went on the air in the early 20th century using radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voices and music via wireless, the medium came to be called "radio." With the advent of television, fax, data communication, and the effective use of a larger portion of the spectrum, the term "wireless" has been resurrected.

Common examples of wireless equipment in use today

• Cellular phones and pagers: provide connectivity for portable and mobile applications, both personal and business
• Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth
• Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless
• Cordless telephone sets: these are limited-range devices, not to be confused with cell phones
• Home-entertainment-system control boxes: the VCR control and the TV channel control are the most common examples; some hi-fi sound systems and FM broadcast receivers also use this technology
• Remote garage-door openers: one of the oldest wireless devices in common use by consumers; usually operates at radio frequencies
• Two-way radios: this includes Amateur and Citizens Radio Service, as well as business, marine, and military communications
• Baby monitors: these devices are simplified radio transmitter/receiver units with limited range
• Satellite television: allows viewers in almost any location to select from hundreds of channels
• Wireless LANs or local area networks: provide flexibility and reliability for business computer users
Wireless technology is rapidly evolving, and is playing an increasing role in the lives of people throughout the world. In addition, ever-larger numbers of people are relying on the technology directly or indirectly. (It has been suggested that wireless is overused in some situations, creating a social nuisance.) More specialized and exotic examples of wireless communications and control include:
• Global System for Mobile Communication (GSM): a digital mobile telephone system used in Europe and other parts of the world; the de facto wireless telephone standard in Europe
• General Packet Radio Service (GPRS): a packet-based wireless communication service that provides continuous connection to the Internet for mobile phone and computer users
• Enhanced Data GSM Environment (EDGE): a faster version of the Global System for Mobile (GSM) wireless service
• Universal Mobile Telecommunications System (UMTS): a broadband, packet-based system offering a consistent set of services to mobile computer and phone users no matter where they are located in the world
• Wireless Application Protocol (WAP): a set of communication protocols to standardize the way that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access
• i-Mode: the world's first "smart phone" for Web browsing, first introduced in Japan; provides color and video over telephone sets

Wireless can be divided into:

• Fixed wireless: the operation of wireless devices or systems in homes and offices, and in particular, equipment connected to the Internet via specialized modems
• Mobile wireless: the use of wireless devices or systems aboard motorized, moving vehicles; examples include the automotive cell phone and PCS (personal communications services)
• Portable wireless: the operation of autonomous, battery-powered wireless devices or systems outside the office, home, or vehicle; examples include handheld cell phones and PCS units
• The use of devices that convey data via IR (infrared) radiation; employed in certain limited-range communications and control systems

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