What is WiMAX ?WiMAX is short for Worldwide Interoperability for Microwave Access. It is a metropolitan wireless standard created by the companies Intel and Alvarion in 2002 and ratified by the IEEE (Institute of Electrical and Electronics Engineers) under the name IEEE-802.16. More precisely, WiMAX is the commercial designation that the WiMAX Forum gives to devices which conform to the IEEE 802.16 standard, in order to ensure a high level of interoperability among them.Goals of WiMAXThe goal of WiMAX is to provide high-speed Internet access in a coverage range several kilometres in radius. In theory, WiMAX provides for speeds around 70 Mbps with a range of 50 kilometres. The WiMAX standard has the advantage of allowing wireless connections between a base transceiver station (BTS) and thousands of subscribers without requiring that they be in a direct line of sight (LOS) with that station. This technology is called NLOS for non-line-of-sight. In reality, WiMAX can only bypass small obstructions like trees or a house and cannot cross hills or large buildings. When obstructions are present, actual throughput might be under 20 Mbps. Operating principle of WiMAXAt the heart of WiMAX technology is the base transceiver station, a central antenna which communicates with subscribers' antennas. The term point-multipoint link is used for WiMAX's method of communication. Fixed WiMAX and WiMAX portableThe revisions of the IEEE 802.16 standard fall into two categories: Fixed WiMAX, also called IEEE 802.16-2004, provides for a fixed-line connection with an antenna mounted on a rooftop, like a TV antenna. Fixed WiMAX operates in the 2.5 GHz and 3.5 GHz frequency bands, which require a licence, as well as the licence-free 5.8 GHz band. Mobile WiMAX, also called IEEE 802.16e, allows mobile client machines to be connected to the Internet. Mobile WiMAX opens the doors to mobile phone use over IP, and even high-speed mobile services.Standard Frequency Speed RangeFixed WiMAX (802.16-2004) 2-11 GHz (3.5 GHz in Europe) 75 Mbps 10 kmMobile WiMAX (802.16e) 2-6 GHz 30 Mbps 3.5 kmApplications of WiMAXOne of WiMAX's potential uses is to cover the so-called "last mile" (or "last kilometre) area, meaning providing high-speed Internet access to areas which normal wired technolgies do not cover (such as DSL, cable, or dedicated T1 lines). Another possibility involves using WiMAX as a backhaul between two local wireless networks, such as those using the WiFi standard. WiMAX will ultimately enable two different hotspots to be linked to create a mesh network.

WiMAX and Quality of ServiceThe WiMAX standard natively supports Quality of Service (often called QoS for short), the ability to ensure that a service works when used. In practice, WiMAX lets bandwidth be reserved for a given purpose. Some applications cannot work properly when bottlenecks occur. This is the case for Voice Over IP (VOIP), as spoken communication is ineffective when gaps a second long are introduced.

WiMAX StandardsStandard Frequency Status Range

IEEE std 802.16Defines wireless metropolitan area networks (WMANs) on frequency bands higher than 10 GHz.

October 2002

Obsolete

IEEE std 802.16aDefines wireless metropolitan area networks on frequency bands from 2 to 11 GHz inclusive.

October 9, 2003

Obsolete

IEEE 802.16bDefines wireless metropolitan area networks on frequency bands from 10 to 60 GHz inclusive.

 Merged with 802.16a (Obsolete)

IEEE std 802.16cDefines options (profiles) for wireless metropolitan area networks in unlicensed frequency bands.

  July 2003

IEEE 802.16d (IEEE std 802.16-2004)

Revision incorporating the 802.16, 802.16a, and 802.16c standards.

October 1st, 2004

Active

IEEE std 802.16eAllows wireless metropolitan area networks to be used by mobile clients.

  not ratified

IEEE std 802.16fAllows wireless mesh networks to be used.

  not ratified

Most people associate the term "Wi-Fi®" with the ability to browse the internet wirelessly. Though this definition isn't incorrect, there is much more to Wi-Fi wireless technology than just browsing the internet. Ten years ago, no one would have thought that it would be possible to listen to music from your basement computer on your entertainment system upstairs, or download songs to your Wi-Fi-enabled MP3 player, but Wi-Fi technology has made it possible to do not only these, but a host of other applications as well. What is Wi-Fi?Short for "wireless fidelity", Wi-Fi is one of the most popular wireless communications standards on the market. In its fledgling stages, Wi-Fi technology was almost solely used to wirelessly connect laptop computers to the internet via local area networks (LANs), but thanks to the immense flexibility the technology provides, that's no longer the case. Wi-Fi technology is now found in a host of non-computer electronic devices as well, such as home theater receivers, portable gaming devices, DVD players, digital cameras, and even GPS devices. Wi-Fi is technically a trademarked brand name for the wireless standard owned by the Wi-Fi Alliance, much like Bluetooth® is trademarked by the Bluetooth Special Interest Group. However, the term has become so widely used (like Xerox® and Kleenex®), that it has become a generic term, and the copyright is no longer protected. Wireless Standards The official name for the specification is IEEE 802.11, and it is comprised of more than 20 different standards, each of which is denoted by a letter appended to the end of the name. The most familiar standards are 802.11b and 802.11g (Wireless B and G) which are used in the majority of commercial Wi-Fi devices. Both of these standards operate in the 2.4 GHz band, and the only major difference between the two is the transfer rate (see chart below).Some consumer electronics, however, use a different standard—Wireless A. These devices operate within the 5 GHz range and have transfer rates equivalent to 802.11g. However, since they operate on different frequencies, devices using the 802.11a standard cannot communicate with B and G-enabled devices. For this reason, it is important to check the compatibility of components with your wireless network prior to purchasing them.Comparison of standards The table below provides a brief overview of the three most popular current 802.11 standards, as well as information about the next version of Wi-Fi — 802.11n.

Standard Frequency Data Transfer Rate Typical (Max) Range (indoor)802.11a 5 GHz 25 (50) Mb/sec about 10 m (30 ft)802.11b 2.4GHz 6.5 (11) Mb/sec 30 m (90 ft)802.11g 2.4 GHz 25 (54) Mb/sec 30+ m (90+ ft)802.11n * 2.4 GHz 200 (540) Mb/sec 50m (150ft)

* The 802.11n standard is not expected to be completed until late 2009.Advantages of Wi-FiUnparalleled mobility and flexibility If you've ever installed a multi-room stereo and had to run wires through a wall, you know the amount of time and effort it requires, not to mention the permanence of your

installation. If you want to move the receiver to another room, the wiring has to be completely redone, and the holes patched.Thanks to Wi-Fi, users are no longer confined by the cords that link their devices, enabling new levels of connectivity without sacrificing function or design options. Many new products, called music streamers, are being introduced that utilize Wi-Fi technology to wirelessly broadcast your music to speakers located throughout your house. Some systems are different than others, but typically you can listen to the same, or different music in each room, play music from the server or any computer attached to the network, and even listen to internet radio. Quick, easy setup Setting up a wireless network may sound like a daunting task, but it's actually a pretty straightforward process. Wi-Fi networks don't require professional installation, and, best of all, there are no holes to drill or wires to run through walls. Many new routers are "plug-and-play," meaning you just connect them to a power outlet, plug in an Ethernet cord, and voilà, your network has been created. Unfortunately, wireless security doesn't automatically configure itself, so it's important to remember to enable it via a personal computer once a connection to the wireless network has been established. (We'll touch on this topic more in-depth in the limitations section.)Fast data transfer rates With transfer speeds up to 54 megabits (Mb) per second (6.75 megabytes), 802.11g is currently the fastest commercially available Wi-Fi protocol on the market. It is important to note that this is the maximum theoretical transfer rate, not that which one should expect on a daily basis. Nonetheless, typical 802.11g networks are more than capable of handling the demands of streaming standard-definition TV signals, as well as CD-quality audio.Limitations of Wi-FiSo far we've covered some of the advantages offered by Wi-Fi wireless technology, but there are some limitations that must be addressed as well. Security and interference are the main issues with current Wi-Fi standards, as well as its inability to reliably stream high definition audio and video.Security concerns Though typically very easy to set up, securing your Wi-Fi network requires more effort. Wi-Fi access points do not come with encryption straight out of the box; you have to do it from your computer once the network is up and running. An unsecured wireless network is susceptible to attacks from hackers, potentially giving them access to all of the information stored by the devices on your network. In addition, "friendly," yet unauthorized computers will also be able to connect to your network, occupying the bandwidth and hindering overall network performance. Interference from other devices Wi-Fi transmissions take place primarily within the 2.4 GHz spectrum, making them susceptible to interference from Bluetooth® wireless enabled devices, cordless telephones, microwave ovens, baby monitors, and other household devices. The farther your Wi-Fi devices are located from these known interferers—and the closer they are to one another—the more robust your signal will be, so keep that in mind during setup.If you live in an apartment complex or in close proximity to your neighbors, their wireless network can also be a source of interference. However, many newer routers

automatically select the channel with the least amount of interference, ensuring that you get the best possible connection.Lack of support for high-quality media streaming Even the fastest current Wi-Fi standards are pushed beyond their limit when trying to handle some of today's high-end media. High-definition audio and video files are bandwidth and timely-delivery-intensive, and typical wireless networks have neither the transfer speeds nor the consistency to transfer them flawlessly. This problem is further compounded if there are multiple devices connected to the same access point because the bandwidth must be divided between all of the equipment.Securing your Wi-Fi networkThe best choice for wireless network encryption is currently Wi-Fi Protected Access (WPA2). Most newer access points support WPA2 encryption, and it can be configured once your network has been set up. For more security tips, check out our article on creating a home network.Bluetooth® wireless technology, on the other hand, has security built in, and it automatically requires devices to enter a passkey in order to connect to the network. See our introduction to Bluetooth for more information on how Bluetooth works.

WiMax to WiFi Network