How WiFi Works

If you've been in an airport, coffee shop, library or hotel recently, chances are you've been right in the middle of a wireless network. Many people also use wireless networking, also called WiFi or 802.11 networking, to connect their computers at home, and an increasing number of cities use the technology to provide free or low-cost Internet access to residents. In the near future, wireless networking may become so widespread that you can access the Internet just about anywhere at any time, without using wires.

WiFi has a lot of advantages. Wireless networks are easy to set up and inexpensive. They're also unobtrusive -- unless you're on the lookout for a place to use your laptop, you may not even notice when you're in a hotspot. In this article, we'll look at the technology that allows information to travel over the air. We'll also review what it takes to create a wireless network in your home.

Wireless Router

What Is WiFi?

A wireless network uses radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens:

1. A computer's wireless adapter translates data into a radio signal and transmits it using an antenna.
2. A wireless router receives the signal and decodes it. It sends the information to the Internet using a physical, wired Ethernet connection.

The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to the computer's wireless adapter.

The radios used for WiFi communication are very similar to the radios used for walkie-talkies, cell phones and other devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s and 0s. But WiFi radios have a few notable differences from other radios:

• They transmit at frequencies of 2.4 GHz or 5GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.
• They use 802.11 networking standards, which come in several flavors:
  
• • 802.11b was the first version to reach the marketplace. It's the slowest and least expensive standard, and it's becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complimentary code keying (CCK) coding.
  • 802.11g also transmits at 2.4 GHz, but it's a lot faster than 802.11b -- it can handle up to 54 megabits of data per second. 802.11g is faster because it uses orthogonal frequency-division multiplexing (OFDM), a more efficient coding technique.
  • 802.11a transmits at 5GHz and can move up to 54 megabits of data per second. It also and uses OFDM coding. Newer standards, like 802.11n, can be even faster than 802.11g. However, the 802.11n standard isn't yet final.
  • WiFi radios can transmit on any of three frequency bands. Or, they can "frequency hop" rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously.

  As long as they all have wireless adapters, several devices can use one router to connect to the Internet. This connection is convenient and virtually invisible, and it's fairly reliable. If the router fails or if too many people try to use high-bandwidth applications at the same time, however, users can experience interference or lose their connections.

  Next, we'll look at how to connect to the Internet from a WiFi hotspot.

  WiFi Hotspots

  If you want to take advantage of public WiFi hotspots or start a wireless network in your home, the first thing you'll need to do is make sure your computer has the right wireless gear. Most new laptops and many new desktop computers come with built-in wireless transmitters. If your laptop doesn't, you can buy a wireless adapter that plugs into the PC card slot or USB port. Desktop computers can use USB adapters, or you can buy an adapter that plugs into the PCI slot inside the computer's case. Many of these adapters can use more than one 802.11 standard.

Once you've installed your wireless adapter and the drivers that allow it to operate, your computer should be able to automatically discover existing networks. This means that when you turn your computer on in a WiFi hotspot, the computer will inform you that the network exists and ask whether you want to connect to it. If you have an older computer, you may need to use a software program to detect and connect to a wireless network.

Being able to connect to the Internet in public hotspots is extremely convenient. Wireless home networks are convenient as well. They allow you to easily connect multiple computers and to move them from place to place without disconnecting and reconnecting wires. In the next section, we'll look at how to create a wireless network in your home.

Building a Wireless Network

If you already have several computers networked in your home, you can create a wireless network with a wireless access point. If you have several computers that are not networked, or if you want to replace your Ethernet network, you'll need a wireless router. This is a single unit that contains:

A port to connect to your cable or DSL modem

1. A router
2. An Ethernet hub
3. A firewall
4. A wireless access point

A wireless router allows you to use wireless signals or Ethernet cables to connect your computers to one another, to a printer and to the Internet. Most routers provide coverage for about 100 feet (30.5 meters) in all directions, although walls and doors can block the signal. If your home is very large, you can buy inexpensive range extenders or repeaters to increase your router's range.

New Mobile Phone

Sony Ericsson Xperia™ X1

Take control of your world with the customizable Xperia™ X1 mobile phone. Access the web, multimedia entertainment and applications with the touch of a finger.

One-touch access to everything.

Enjoy access to different experiences – Web, multimedia, applications – from your X1. Navigate with the tip of your finger. Configure and have your X1 panels just the way you want them.

• 

• Sony Ericsson panel

  – Customize your X1 with information about the time and weather, news feeds, calendar updates, messaging status and much more5.

• Media Experience panel

  – Seamlessly navigate through captured photos and video clips, pictures, photo tags, games, music, videos, and more. The Media Experience panel also enables easy navigation to both local and Web content, and makes it possible for users to create playlists or browse through their favorite tracks.

• Google panel

  – Do a quick search, access your Gmail or find the way via Google Maps

• Microsoft Today panel

  – This panel provides the Windows experience – it allows you to navigate your phone just like in other Windows devices

• 3D Fish panel

  – Fish in your phone that react to taps on the screen? Yep, that's it. And they're not just for fun, they're helpful too – the fish let you know when you've missed a call and indicate when your phone's on silent.

• FM radio panel
  

  – Plug in your headset, touch the radio panel and enjoy your favorite FM station

• Slideshow panel

  Displays a slideshow of recently taken videos and photos.

• Panels can be organized the way you like and new panels can be added with the touch of your finger. You can download new panels from Sony Ericsson as they become available or develop your own panels for the ultimate in personalization.

Sharp looks.

The X1 offers a sophisticated and distinctive design complete with a premium metal body, a 3-inch touch screen display, and an arc slider design for the finest viewing angle while using the slide out QWERTY keyboard.

Take the office with you.

Work efficiently on the go with your Xperia™ X1. Connect easily to your office using the familiar Windows interface to manage your email, calendar, and Microsoft Office documents, such as Excel, Word, and PowerPoint®. Browse the web and receive RSS feeds with mobile internet, or for a fast connection in hotspots, utilize Wi-Fi support .

How may we help you?

Your X1 Support Card (included with purchase of an X1) is your access to a dedicated network for X1 users, helping you get the most out of your X1. X1 Support includes both telephone support and web support in the United States and abroad. You can call one of our specialist teams or log on to learn more about your X1 or to solve issues you may have.

Everywhere entertainment.

Enjoy your favorite entertainment in a variety of ways. The Xperia™ X1 offers a digital camera and video capture to catch those unexpected and memorable moments. Use the music player to listen to downloaded music, and the video player to play recorded or downloaded video clips from websites like YouTube. Create playlists or browse through your content of photos, videos, pictures, photo tags, games and more.

LED Can Do More

Sony XEL-1 OLED TV

Sony shows their first commercial OLED TV named XEL-1.
The XEL-1 is now available in the USA at the SonyStyle store for 2.500 Dollar



Sony's OLED (Organic Light Emitting Diode) TV, the XEL-1, is truly the next big thing in television technology.
The XEL-1 is an 11 inch display that is only 3mm thin. The measurements of the XEL-1 are 287×253×140mm.
Sony has put the ultra-thin display on a pedestal with a flexible arm. At 11 inch the Sony XEL-1 is a nice stylish desk accessory.
which weighs two kilograms and is about 3mm thin, features a resolution of 940×540 and contrast ratio of 1,000,000:1, stated Sony.



It boasts a 3 millimeter thin panel and offers unparalleled picture quality with amazing contrast, outstanding brightness, exceptional color reproduction, and a rapid response time. It delivers astounding performance in all the key picture quality categories. OLED technology can completely turn off pixels when reproducing black, resulting in more outstanding dark scene detail and a contrast ratio of 1,000,000:1. OLED also creates unmatched color expression and detail and enables rapid response times for smooth and natural reproduction of fast moving images like those found in sports and action movies. The XEL-1 features the latest connectivity options including two HDMI™ inputs, a digital tuner, and a Memory Stick® media slot for viewing high-resolution photos.

Blazing Fast Response Time
When turned “on,” individual organic elements are stimulated directly by electric current, and therefore response time is incredibly fast.

Exceptional Color Reproduction
Sony’s unique “Super Top Emission” technology, which combined with a special mircro-cavity and color filters, enhances color purity, achieves extraordinary high color contrast. In fact, 105% of the NTSC color space can be achieved!

Energy Efficiency
OLED technology delivers a more efficient means of utilizing light, which is generated by the organic material itself instead of an always on backlight; also, when elements are in their “off” state, they consume no power whatsoever.

The XEL-1 will be exhibited at the Sony exhibition booth at Ceatec Japan 2007 starting from October 2.

The first Sony OLED TV has a resolution of 960x ×540px, but takes input resolution up to 1080p.
The Sony XEL-1 has an integrated digital TV tuner for Japan. Other features of the Sony OLED TV include USB, LAN interface, 1x HDMI port, headphone plug and S-Force sound.

Sony plans to start shipping the XEL-1 OLED TV on December 1st for 200,000 Yen (~$1,740). This is a very high price for an 11 inch TV, but it is the first OLED TV to buy. Early adoption always had its price.
The new OLED TV will last 30,000 hours, about 10 years for someone using the TV eight hours a day. An equivalent Sony LCD TV lasts twice that long, Sony said.




Product Specifications



Video

* Video Signal : 480i, 480p, 720p, 1080i/60, 1080p/60

Weights and Measurements

* Dimensions (Approx.) : 11 5/6 x 9 15/16 x 5 1/2" (287 x 253 x 140mm) with stand

* Weight (Approx.) : 4 lbs 3 oz (1.9Kg) with stand

Audio Features

* Auto SAP : Yes

* Digital Amplifier : Yes

* Dolby® : Dolby® Digital (AC3/ATSC only)

* MTS Stereo Decoder : Yes

* Sony Original Surround : Surround (On, Off)

* Sound Booster : Yes

* Sound Mode : Dynamic, Standard, Custom

* SteadySound® Automatic Volume Control : Yes

* Stereo System : A/V Sync
General

* Color : Black

* Television Type : OLED Flat Panel

Convenience Features

* Favorite Channel : Yes

* ID-1 Detection : Yes

* LightSensor™ Technology : Yes

Video Features

* Picture Adjustment : Mode, Reset, Picture, Brightness, Color, Hue/Color, Temperature, Sharpness, Noise Reduction, MPEG Noise Reduction, Advanced Settings: Black Corrector, Gamma, Clear White, Color Space, Live Color

* 3D Comb Filter : Yes

* Acceptable Video Signals : 480i, 480p, 720p, 1080i/60, 1080p/60

* CineMotion® Reverse 3:2 Pulldown Technology : Yes (Off, Auto)

* Display Technology : OLED

* Noise Reduction : Yes

* Picture Mode : Vivid, Standard, Custom

* Wide Mode : Wide Zoom, Normal, Full, Zoom

Inputs and Outputs

* Digital Audio Output(s) : Yes (Optical)

* HDMI™ Connection Input(s) : 2 (Rear) supports 1080p/60, CEC capable

* HDMI™ Connection(s) (Total) : 2 (Rear)

* HDMI™ Connection(s) (w/ Analog Audio In) : supports 1080p/60, CEC capable

* Headphone Output(s) : 1 (Side)

* Memory Stick® Media Slot : Yes (Memory Stick PRO™)

* RF Connection Input(s) : 1 (rear)

Display

* Aspect Ratio : 16:9

* Dynamic Contrast Ratio : > 1,000,000:1

* Screen Size (measured diagonally) : 11"

* Native Resolution : 960(H) x 540(V)

* Display Resolution : 960(H) x 540(V)

General Features

* Closed Captions (CC) : Yes

* On-Screen Display : XMB®

Service and Warranty Information

* Limited Warranty Term : 1 Year Parts / 1 Year Labor. See Warranty card for full details.

Audio

* Audio Power Output : 2W (1W + 1W)

TTV System

* Channel Coverage : CATV

* Tuner (Terrestrial) : NTSC, CATV, ATSC

* Tuner (Cable) : Clear QAM1

The Best Power Saving Option

LEDs may be little, but new high-brightness models are producing a considerable amount of light.

First used as status and indicator lamps, and more recently in under-shelf illumination, accent lighting, and directional marking applications, high-brightness LEDs have emerged within the last six years. But only recently have they been seriously looked upon as a feasible option in general purpose lighting applications. Before you recommend or install this type of lighting system, you should understand the basic technology upon which these devices are based.
Light-emitting diodes (LEDs) are solid-state devices that convert electric energy directly into light of a single color. Because they employ “cold” light generation technology, in which most of the energy is delivered in the visible spectrum, LEDs don't waste energy in the form of non-light producing heat. In comparison, most of the energy in an incandescent lamp is in the infrared (or non-visible) portion of the spectrum. As a result, both fluorescent and HID lamps produce a great deal of heat. In addition to producing cold light, LEDs:

* Can be powered from a portable battery pack or even a solar array.

* Can be integrated into a control system.

* Are small in size and resistant to vibration and shock.

* Have a very fast “on-time” (60 nsec vs 10 msec for an incandescent lamp).

* Have good color resolution and present low, or no, shock hazard.

The centerpiece of a typical LED is a diode that is chip-mounted in a reflector cup and held in place by a mild steel lead frame connected to a pair of electrical wires. The entire arrangement is then encapsulated in epoxy. The diode chip is generally about 0.25 mm square. When current flows across the junction of two different materials, light is produced from within the solid crystal chip. The shape, or width, of the emitted light beam is determined by a variety of factors: the shape of the reflector cup, the size of the LED chip, the shape of the epoxy lens and the distance between the LED chip and the epoxy lens. The composition of the materials determines the wavelength and color of light. In addition to visible wavelengths, LEDs are also available in infrared wavelengths, from 830 nm to 940 nm.

The definition of “life” varies from industry to industry. The useful life for a semiconductor is defined as the calculated time for the light level to decline to 50% of its original value. For the lighting industry, the average life of a particular lamp type is the point where 50% of the lamps in a representative group have burned out. The life of an LED depends on its packaging configuration, drive current, and operating environment. A high ambient temperature greatly shortens an LED's life.

Additionally, LEDs now cover the entire light spectrum, including red, orange, yellow, green, blue, and white. Although colored light is useful for more creative installations, white light remains the holy grail of LED technology. Until a true white is possible, researchers have developed three ways to deliver it:

* Blend the beams. This technique involves mixing the light from multiple single-color devices. (Typically red, blue, and green.) Adjusting the beams' relative intensity yields the desired color.

* Provide a phosphor coating. When energized photons from a blue LED strike a phosphor coating, it will emit light as a mixture of wavelengths to produce a white color.

* Create a light sandwich. Blue light from one LED device elicits orange light from an adjacent layer of a different material. The complementary colors mix to produce white. Of the three methods, the phosphor approach appears to be the most promising technology.

Another shortcoming of early LED designs was light output, so researchers have been working on several methods for increasing lumens per watt. A new “doping” technique increases light output several times over compared to earlier generations of LEDs. Other methods under development include:

* Producing larger semiconductors.

* Passing larger currents with better heat extraction.

* Designing a different shape for the device.

* Improving light conversion efficiency.

* Packaging several LEDs within a single epoxy dome.

One family of LEDs may already be closer to improved light output. Devices with enlarged chips produce more light while maintaining proper heat and current management. These advances allow the units to generate 10 times to 20 times more light than standard indicator lights, making them a practical illumination source for lighting fixtures.

Before LEDs can enter the general illumination market, designers and advocates of the technology must overcome several problems, including the usual obstacles to mainstream market adoption: Industry-accepted standards must be developed and costs must be reduced. But more specific issues remain. Things like lumen-per-watt efficacy and color consistency must be improved, and reliability and lumen maintenance should be addressed. Nevertheless, LEDs are well on their way to becoming a viable lighting alternative.

DC World

waruna karunsinghe



Edison was right; direct current is better than alternating current. Tesla and Westinghouse won the current wars, because it was easy to transform into different voltages without electronics, and they needed high voltages, which travel longer distances in smaller wires than low voltage.

Our current system is based on big, central power plants like Niagara Falls shown above, that pump out high voltage (as much as 400,000 volts), step it down to 22 thousand volts for distribution at street level, then down to 110/220 for distribution to our houses. At every step, there are transmission losses; as much as 10% of the electricity transmitted by the power plant is lost on the way. The losses are higher in AC than in DC because it grounds so easily; according to the Economist, DC distribution is far more efficient. (Treehugger here)

And then we get to our homes and offices....



...where there is a 110VAC outlet every 12 feet on our wall, switched outlets in our ceilings, all feeding expensive copper wires back to a central panel. And what is plugged into almost every one? Wall warts, transformers converting to a variety of voltages keyed to specific small appliances and electronics. For we now live in an electronic world, and almost everything we use other than vacuum cleaners and kitchen appliances are now running on DC Of course there is no standard of wall wart; every computer, lamp, radio or LCD TV has a different size and voltage. And every wall wart wastes energy in the process.



Lighting, now mostly incandescent needing lots of power, is going low voltage DC as we convert to LED and CFL; every fixture and even bulbs are filled with rectifiers and transformers to convert the power to low voltage, using resources in the manufacturing, and wasting energy in the operation.



For those who want to reduce their consumption and generate a little power of their own with a solar panel or wind turbine, standard practice is to run the 12 DC volt output through an inverter to change it to 110 AC for distribution through the existing 110V wiring. Of course the inverter is not 100% efficient and what are we doing at 90% of the electric outlets? Plugging in a wall-wart and converting it back to low voltage.



When he was designing the MiniHome, Andy Thomson thought this was dumb, and chose all of his lighting to run off 12VDC, cutting off the transformers and wiring it directly to the batteries. He found a Creative sound system that ran at 12V and cut off the wall-wart. The inverter broke and he barely noticed, because everything in the joint but the microwave oven could run off 12VDC.



The Google boys, Sergei and Larry, think this is dumb too. Engineers at Google, tired of running tens of thousands of computers with inefficient power supplies, have proposed a new standard for "high efficiency power supplies for home computers and servers" based on everything running on 12 volts only. They say that it would save 40 billion kwh over three years, worth $5 Billion. Founder Larry Page complained about this last year: “I’m going to just plead with all of you, let’s get the power supply problems fixed, or let’s get all these devices talking together”

John Laumer has noted here that 12 Volt appliances are easier to supply alternate emergency power if you are knocked off the grid by a hurricane or other disaster.

It is time for our codes and our wiring to reflect this, shall we say, transformation. It is time for big steps:

1) Develop a universal standard around 12 volt dc for all electronics. Enough of this silliness that makes every wall wart a different voltage. There will still be different sizes as there are different power requirements, but agree on one voltage.

2) Develop a standard wall plug or distribution system for 12 volt DC. It is ridiculous that the only standard plug for this voltage is the automotive cigarette lighter.

3) Provide a secondary wiring system in all new houses at 12V DC based on the new plug.

4) Revise our current wiring codes to reduce the number of 110V outlets and circuits required. Now most electrical codes demand outlets every 12 feet, in every ceiling, duplex outlets in kitchens. Copper is expensive and its mining is destructive; if there is 12VDC wiring then an outlet per room for the vacuum cleaner is all that is needed. That way, there can be dual systems in a house without any more copper than is needed now.


12VDC power needs no childproofing, no wall warts, creates no EMF and makes adding incremental sources like solar and wind much easier. Let's make it the standard.