Apr 18, 2009

WiMAX Technology at Home

WiMAX Technology at Home
Here's what would happen if you got WiMAX. An Internet service provider sets up a WiMAX base station 10 miles from your home. You would buy a WiMAX-enabled computer or upgrade your old computer to add WiMAX capability. You would receive a special encryption code that would give you access to the base station. The base station would beam data from the Internet to your computer (at speeds potentially higher than today's cable modems), for which you would pay the provider a monthly fee. The cost for this service could be much lower than current high-speed Internet-subscription fees because the provider never had to run cables.

If you have a home network, things wouldn't change much. The WiMAX base station would send data to a WiMAX-enabled router, which would then send the data to the different computers on your network. You could even combine WiFi with WiMAX by having the router send the data to the computers via WiFi.

WiMAX doesn't just pose a threat to providers of DSL and cable-modem service. The WiMAX protocol is designed to accommodate several different methods of data transmission, one of which is Voice Over Internet Protocol (VoIP). VoIP allows people to make local, long-distance and even international calls through a broadband Internet connection, bypassing phone companies entirely. If WiMAX-compatible computers become very common, the use of VoIP could increase dramatically. Almost anyone with a laptop could make VoIP calls.

Network Scale
The smallest-scale network is a personal area network (PAN). A PAN allows devices to communicate with each other over short distances. Bluetooth is the best example of a PAN.
The next step up is a local area network (LAN). A LAN allows devices to share information, but is limited to a fairly small central area, such as a company's headquarters, a coffee shop or your house. Many LANs use WiFi to connect the network wirelessly.

WiMAX is the wireless solution for the next step up in scale, the metropolitan area network (MAN). A MAN allows areas the size of cities to be connected.

WiMAX Cost

A citywide blanket coverage of wireless Internet access sounds great, but companies aren't going to go around setting up WiMAX base stations out of sheer kindness. Who's going to pay for WiMAX?

It depends how it will be used. There are two ways WiMAX can be implemented -- as a zone for wireless connections that single users go to when they want to connect to the Internet on a laptop (the non-line-of-sight "super WiFi" implementation), or as a line-of-sight hub used to connect hundreds of customers to a steady, always-on, high-speed wireless Internet connection.

Under the "super WiFi" plan, cities might pay to have WiMAX base stations set up in key areas for business and commerce and then allow people to use them for free. They already do this with WiFi, but instead of putting in a bunch of WiFi hot spots that cover a few hundred square yards, a city could pay for one WiMAX base station and cover an entire financial district. This could provide a strong draw when city leaders try to attract businesses to their area.

Some companies might set up WiMAX transmitters and then make people pay for access. Again, this is similar to strategies used for WiFi, but a much wider area would be covered. Instead of hopping from one hot spot to another, WiMAX-enabled users could have Internet access anywhere within 30 miles of the WiMAX base station. These companies might offer unlimited access for a monthly fee or a "pay as you go" plan that charges on a per-minute or per-hour basis.

The high-speed wireless hub plan has the potential to be far more revolutionary. If you have high-speed Internet access now, it probably works something like this: The cable (or phone) company has a line that runs into your home. That line goes to a cable modem, and another line runs from the modem to your computer. If you have a home network, first it goes to a router and then on to the other computers on the network. You pay the cable company a monthly fee, which reflects in part the expense of running cable lines to every single home in the neighborhood.

WiMAX Coverage and Speed

WiMAX operates on the same general principles as WiFi -- it sends data from one computer to another via radio signals. A computer (either a desktop or a laptop) equipped with WiMAX would receive data from the WiMAX transmitting station, probably using encrypted data keys to prevent unauthorized users from stealing access.

The fastest WiFi connection can transmit up to 54 megabits per second under optimal conditions. WiMAX should be able to handle up to 70 megabits per second. Even once that 70 megabits is split up between several dozen businesses or a few hundred home users, it will provide at least the equivalent of cable-modem transfer rates to each user.

The biggest difference isn't speed; it's distance. WiMAX outdistances WiFi by miles. WiFi's range is about 100 feet (30 m). WiMAX will blanket a radius of 30 miles (50 km) with wireless access. The increased range is due to the frequencies used and the power of the transmitter. Of course, at that distance, terrain, weather and large buildings will act to reduce the maximum range in some circumstances, but the potential is there to cover huge tracts of land.

IEEE 802.16 Specifications
Range - 30-mile (50-km) radius from base station
Speed - 70 megabits per second
Line-of-sight not needed between user and base station
Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands)
Defines both the MAC and PHY layers and allows multiple PHY-layer specifications

How WiMAX Works

In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to those remote locations.

A WiMAX system consists of two parts:

A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles (~8,000 square km).
A WiMAX receiver - The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today.

A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection (for example, a T3 line). It can also connect to another WiMAX tower using a line-of-sight, microwave link. This connection to a second tower (often referred to as a backhaul), along with the ability of a single tower to cover up to 3,000 square miles, is what allows WiMAX to provide coverage to remote rural areas.

What this points out is that WiMAX actually can provide two forms of wireless service:

There is the non-line-of-sight, WiFi sort of service, where a small antenna on your computer connects to the tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength transmissions are not as easily disrupted by physical obstructions -- they are better able to diffract, or bend, around obstacles.
There is line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more bandwidth.
WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square mile s or 65 square km of coverage, which is similar in range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers or routers set up within the transmitter's 30-mile radius (2,800 square miles or 9,300 square km of coverage). This is what allows WiMAX to achieve its maximum range.

The final step in the area network scale is the global area network (GAN). The proposal for GAN is IEEE 802.20. A true GAN would work a lot like today's cell phone networks, with users able to travel across the country and still have access to the network the whole time. This network would have enough bandwidth to offer Internet access comparable to cable modem service, but it would be accessible to mobile, always-connected devices like laptops or next-generation cell phones.

Limitations OF wiMAX

A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 50 kilometers (~31 miles). In reality, WiMAX can either operate at higher bitrates or over longer distances but not both: operating at the maximum range of 50 km increases bit error rate and thus results in a much lower bitrate. Conversely, reducing the range (to <1m) allows a device to operate at higher bitrates. There are no known examples of WiMAX services being delivered at bit rates over around 3 Mbit/s.
Typically, fixed WiMAX networks have a higher-gain directional antenna installed near the client (customer) which results in greatly increased range and throughput. Mobile WiMAX networks are usually made of indoor "Customer-premises equipment" (CPE) such as desktop modems, laptops with integrated Mobile WiMAX or other Mobile WiMAX devices. Mobile WiMAX devices typically have omnidirectional antennae which are of lower-gain compared to directional antennas but are more portable. In current deployments, the throughput may reach 2 Mbit/s symmetric at 10 km with fixed WiMAX and a high gain antenna. It is also important to consider that a throughput of 2 Mbit/s can mean 2 Mbit/s, symmetric simultaneously, 1 Mbit/s symmetric or some asymmetric mix (e.g. 0.5 Mbit/s downlink and 1.5 Mbit/s uplink or 1.5 Mbit/s downlink and 0.5 Mbit/s uplink), each of which required slightly different network equipment and configurations. Higher-gain directional antennas can be used with a WiMAX network with range and throughput benefits but the obvious loss of practical mobility.
Like most wireless systems, available bandwidth is shared between users in a given radio sector, so performance could deteriorate in the case of many active users in a single sector. In practice, most users will have a range of 2-3 Mbit/s services and additional radio cards will be added to the base station to increase the number of users that may be served as required.
Because of these limitations, the general consensus is that WiMAX requires various granular and distributed network architectures to be incorporated within the IEEE 802.16 task groups. This includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

How to Build a WiMAX Network

The latest technology buzz is WiMAX wireless networks. We have heard many things about this wonderful new long haul wireless technology that it almost seems as though you are just a phone call away from having yours' designed and installed. Well before you start assuming things like we all do, we thought as engineers and network architects we would share personal experiences and the experiences of colleagues from around the world, in a manner that is direct, helpful, educational, and certainly reality based. This is a backpocket Primer for anyone now dealing with the implementation of a WiMAX network.

First, there are several misconceptions surrounding WiMAX that need to be cleared up so that the business aspects and engineering basis have a common understanding.

Secondly, the people who make the various decisions within your organizations need to understand that there are differences between a private network and an interoperable network strategy. This subtle difference does exist and requires a plan which considers the final transition aspects, if considered now, to easily provide a lower cost upgrade to a true interoperable network, now incorporating diverse vendor equipment.

Finally, while WiMAX has been out internationally for several years, it is very new to the United States, only a few months old, with very little training and education available to those who have the responsibility to build these systems or those who will make the financial and technical decisions to have these systems built for them as part of their long haul wireless strategy.

Our experiences and the experiences of our collegues are offered here as contributions as well as tying these in to the standards and certification authorities all meant to provide a reality based quick reference education for anyone in the throws of How to Build a WiMAX network.


WiMAX is a standard designed for fixed broadband wireless access featuring a controlling base station, that connects subscriber stations not to each other but to various public networks, such as the Internet, linked to that base station. The acronym means “ worldwide interoperability for microwave access” or (WiMAX).

WiMAX, as a standards initiative, is based on a "set of profiles" supporting a wide range of frequencies (up to 66GHz)with channel sizes (1.25MHz to 20MHz) and applications (LOS and NLOS), and finally PTP and PTMP. The WiMAX profiles narrow the scope of 802.16 to focus on first service specific configurations. The IEEE titled the specification 802.16 and released it December 2002. The profiles addressed in that “profiles release” are 802.16-2004 (old d) and 802.16e as presented further down.

The WIMAX forum was formed eight months earlier in April 2002 to support, promote and certify compatibility and interoperability of devices based on the 802.16 specification, and to develop such devices for the marketplace. Founding Members of the organization include Airspan, Alvarion, Analog Devices, Aperto Networks, Ensemble Communications, Fujitsu, Intel, Nokia, OFDM Forum, Proxim, and Wi-LAN.

WiMAX is the IEEE 802.16 Point-to-Multipoint broadband wireless access standard for systems in the stated frequency ranges. WiMAX will initially provide fixed nomadic, portable and eventually, mobile wireless broadband connectivity. To that end there are two standards (802.16d (new -2004) and 802.16e respectively) although they will both perform similar functions because they must be interoperable. One clearly is a fixed solution and the other a mobile solution that must still communicate with a fixed solution. So one of the first considerations is whether you want to build out a mobile or fixed network. In many cases you would have already considered your target market segments, spectrum availability, regulatory constraints and your deployment need.

Which One do I Need?

Generally speaking, the current 802.16-2004 (originally 802.16d) fixed network products are less complex than 802.16e mobile network systems because; they can be used in a wider range of unlicensed bands, they offer a faster time-to-market, and in many cases a higher throughput than 802.16e equipment. On the other hand, there is better support for mobility and a wider range of terminal form factors advantages of 802.16e equipment.

It’s certainly a consideration but no matter what you chose the migration paths to move in either direction are easily achieved through overlay networks, software upgradeable base stations, dual mode devices and dual mode base stations. This consideration assures you are not stuck in one mode or the wrong mode and that your initial investment is protected. Makes the CTO and CEO happy.

WiMAX base stations transmit up to 30 miles, but because it is a cell-based topology, would yield a more typical range of 3 to 5 miles. WiMAX systems can deliver a capacity of up to 75 Mbps per channel, for fixed and portable access applications. This is enough bandwidth to simultaneously support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity as we have seen.

WiMAX technology will be incorporated in portable computers and PDAs expected in late 2006 and early 2007, allowing for urban areas and cities to become “MetroZones”, the new buzz word, for portable outdoor broadband wireless access. In addition, Wireless service providers and telecommunication equipment industries are embracing WiMAX technology because of its tremendous cost advantages to provide that last-mile connectivity to large parts of the world that are too expensive to serve with wired technologies requiring all that trenching.


Due to the security issues with WEP in the 802.11 Wi-Fi arenas, the standards bodies took no chances with WiMAX, and wisely prioritized security from the onset. Base station designers went to work to assure a dedicated high performance security processor. The WiMAX security standard requires that all traffic be encrypted with CCMP (which is Counter Mode with Cipher Block Chaining Message Authentication Code Protocol).

According to the WiMAX forum, the group's aim is for end-to-end authentication. WiMAX uses PKM-EAP (Extensible Authentication Protocol), which relies on the TLS standard following public key cryptography. Having addressed this level of security from the start provides an excellent reference point to add multi-level security options as well, if your implementation requires an MLS approach. Secure (blacker) implementations would require such an approach.

What is Released?

The first certification release for 802.16-2004 fixed is out there already and includes products from certified vendors with two profiles in the 3.5GHz and the 5.8GHz bands supporting fixed and nomadic access. The profiles for 802.16e mobile are not available nor released as of this writing but are expected to be in the ranges of 2.3GHz to 2.5GHz when officially released. WiMAX profiles based on 802.16-2004 are better suited to fixed applications that use directional antennas because OFDM is inherently less complex than SOFDMA used in the mobile application. As a results, 802.16-2004 networks will be deployed much faster and at a lower cost. Our experiences are with these released systems in the US and around the world in ground applications, mobile military, public safety and maritime applications.

Planning for WIMAX

Companies, cities or projects in maritime or ground systems in the US that have decided to or are considering building and operating a WiMAX network will have a few important issues to consider. The initial spectrum for WiMAX in the USA is unlicensed spectrum in the 5GHz range. Given this spectrum is open it will have inherent interference issues and risks which will require attention. There are many ways of overcoming interference issues. The answers come from a proper site selection, following your RF survey training and from the actual selected equipment. So, the planning and site survey results remain the key to your confident success.


WiMAX provides optimized solutions for fixed, nomadic, portable and mobile broadband wireless access. There are two flavors in various release and implementation modes. The first is 802.16-2004 WiMAX with two initial frequency profiles – the 3.5GHz and the 5.8GHz bands supporting fixed and nomadic access in LOS and NLOS environments now. The other flavor is 802.16e WiMAX with expected profiles in the 2.3GHz and 2.5GHz ranges optimized for dynamic mobile radio channels supporting hands-ff and roaming --arriving by 2007. Another exciting technology for all of us. Have fun!

Wi-fi and Wi-max - Why You Shouldn't Use Them

The hot new craze in Internet access is Wi-Fi and its soon-to-be big brother Wi-Max. Wi-Fi is a wireless connection that allows users to access the Internet without the computer being connected to a cable. And yes, it's very convenient. Imagine walking from the sofa to the bedroom with your laptop and never loosing your connection. Imagine the freedom and flexibility afforded schools and office workers. No more ugly bothersome cables to tie you down. You're free to roam the Internet with your fingers while roaming your home, school or office with your feet. Freedom to move and freedom to surf. Perfect for the individual who is on the go and up to date with the latest technology. You can even have free Internet access at your local coffee shop. Same for airports. What a great idea. Or is it?

What exactly is Wi-Fi? Wi-Fi is a common term that stands for 'wireless fidelity.' It simply means that a computer can access the Internet without wires or cables. In other words, it allows one to have a wireless connection to the Internet. It's like taking a cell phone base station and placing it in your home, schoolroom or office area. Wi-Fi is basically the same type of connection as used to operate a cell phone. It's a product of convenience as it allows one to access the Internet with a desktop or laptop computer without the need for connecting cables. Moving from room to room with a laptop computer and no cables is a nice convenience although it certainly isn't a necessity.

How does Wi-Fi work? Wi-Fi is really very similar to your cell phone. Radio signals are transmitted from the computer or Bluetooth device to a wireless router, sometimes called a wireless access point (WAP) or wireless local area network (WLAN). The router then sends the signal to the Internet through a cable modem. So this router or wireless access point is really the device responsible for transmitting the harmful radio waves. Any number of computers or devices can be configured to connect to one wireless router to make Internet connections. The workable distance is about a range of 300 feet or more from the wireless access point while most distances for good connections are maintained at about 100 feet. And, of course there are many variables that can affect this connection. Laptop computers and Personal Digital Assistants (PDAs) are the most common devices utilizing Wi-Fi technology.

Wi-Fi Emits Radio Frequencies Wireless connections emit radio frequency signals, or radiation, just like cell phones, cell phone towers and other wireless devices. Wi-Fi usually transmits its signal at frequencies in the range of 2.4GHz to 5 GHz. Cordless phones often transmit in the 2.4GHz to 5 GHz range, too, and this often causes the cordless phone to interfere with a wireless internet connection to a nearby computer. The Wi-Fi frequency is considerably higher than the frequencies used for cell phones which operate in the 850 MHz to1900 MHz range. This higher frequency allows more data to be carried. However, as we'll see later, it is not the frequency of the signal that does the damage to our health. So the higher Wi-Fi frequency isn't really the issue at all when it comes to health considerations.

Wi-Fi Hotspots Now In Schools Wi-Fi has become popular in the home, office, the airport and coffee shops. Many cities are now installing "hot spots" where one can take a laptop computer and freely access the Internet over the provided network. This is what is known as a "hot spot." It's a place to make a wireless connection to the Internet. And they are springing up everywhere. Entire cities are becoming wireless allowing one to connect to the Internet from anywhere in the city. And due to the ease of convenience Wi-Fi connections in schools are now becoming quite popular, too. No longer are computers hard-wired to a connection in a classroom. Connections are now virtual and allow the user, student or teacher, the freedom to connect anywhere in the school without the burden of being restricted by cable connections.

Why Wireless Connections Are Harmful There are two potentially harmful mechanisms in which Wi-Fi users, including school children, may be harmed. The first mechanism involves the exposure to radiation from the distance or proximity of the user to the computer monitor. This form of exposure originates from the electromagnetic field being given off by the monitor itself and has nothing to do with the wireless connection. Electromagnetic radiation is given off by the computer screen regardless of whether the connection is wired or wireless. Any and all computer screens produce electromagnetic radiation. These electromagnetic fields can be substantial in strength and can reach levels much higher than the 1 milligauss (1 mG) threshold level of exposure recommended by experts as being safe. Such a field can easily be measured with an inexpensive instrument called a gauss meter.

The second mechanism of harm comes from the radiation or radio wave itself. The wireless signal, oscillating at 2.4 to 5 GHz, moves much too fast for the body to recognize. So this wave isn't doing the damage. However, anytime any data or information is transmitted, say through our voice, through text messages or through the sending of information, the data is packaged and "piggy-backed" onto the first wave. This creates a second carrier wave and this wave is called the information-carrying radio wave, or ICRW. It is the information-carrying radio wave that is producing the harm. Here's how this happens. This second carrier wave, or ICRW, oscillates in a much lower Hertz (Hz) range that is easily recognized by the body. When the ICRW comes in contact with the body the body recognizes this wave and responds to it as if this carrier wave were some type of foreign invader. When this happens certain physiologic changes occur which are very significant. First, at the cellular level, the cell membrane becomes hard and inflexible. This occurs because the active transport channels shut down as the cell goes into a protection mode. This hardening effect of the cell membrane also causes the cell to lose its permeability, meaning needed nutrients can't get inside the cell where they are needed. In other words, the cell doesn't get nourished.

Conversely, since the cell membrane is hardened and less permeable, the toxins and free radicals that build up inside the cell, as a natural part of our daily metabolism, can't get out. The buildup of toxins and free radicals inside the cell causes other problems. These toxic products damage the mitochondria in the cell. If you'll remember from biology class the mitochondria are where energy for the body is produced. When this energy-producing process is damaged the cell begins to lose its ability to function.

In addition, cells lose their ability to communicate with one another. When one cell can't communicate with another cell and messages don't get sent or received the body can't respond properly to any type of stress, injury, or invasion. Furthermore, the DNA inside the cell becomes damaged. Fragments of DNA break off and form something called micronuclei. Micronuclei are precursors to cancer formation. And when enough energy is lost and when enough malnourishment occurs the cell eventually becomes dysfunctional and dies. When enough cells die the tissues are affected. When enough tissue is affected organs become damaged and don't work properly. And the cascade of damaging events begin that can lead to a multitude of symptoms and failure of the body's defense mechanisms to act appropriately.

The Wi-Fi Problem Think of Wi-Fi this way. It's really nothing more than a small version of a cell phone tower placed in the classroom or office. Or, it could be similar to having a cordless phone in your home with multiple handsets throughout the house. The base station is the access point and all the peripheral phones connect with it wirelessly. The radio frequency radiation being emitted is the same. The information-carrying radio wave is being transmitted continuously 24 hours a day. The connections from the computers and other wireless devices throughout the school, office or home to the wireless access points cause any user around them, (children, teacher, staff, etc.) to be continuously exposed. Everyone in the building is caught in the crossfire of the continual access to the wireless access points. Even non-users are exposed because of the blanketing effect of these wireless access points throughout the building. So no one escapes the exposure.

In understanding the danger of Wi-Fi we must remember that it is not the type of device, in this case a wireless access point or router that is important. Rather it is the type of radio frequency radio waves that are being produced by the device that are significant. Whether from a wireless router, a cell phone, a cell phone tower, or personal digital assistant (PDA), electromagnetic frequencies are produced by all these devices. We must look at the technology being used by these devices and not the device itself as the problem. This should be the primary concern as we evaluate their safety, particularly in the classroom.

Another important aspect of Wi-Fi exposure is that of modulation. Modulation refers to whether or not the signal frequency is constant or pulsed. The new digital cell phones operate on a pulsed frequency, as does all wireless technology. Studies have shown that these pulsed signals are a greater risk than analog, non-pulsed signals. 1

Certainly, by the addition of any type of wireless we are adding to the burden of electropollution we are all currently exposed to. Special consideration should be given to the additional exposure that Wi-Fi technology would bring to those in a classroom, including the instructors, teachers, staff and certainly students.

Children Are More Vulnerable Concern about the increased vulnerability to electropollution by children has valid reasoning. Since the skull bones of the head don't fully harden until about age 22 the skull bones of a child's head are softer than that of an adult. A softer head bone translates to easier penetration through the skull and into the head by radio frequency radiation. Furthermore, the head of a child contains more water since the brain is not fully developed. It would make sense then that water will act as a conductor to electromagnetic radiation increasing the possibility of even further damage. And since a child's brain and nervous system is still developing it only stands to reason that the potential damage would be greater since cells that are in a growing phase are more easily damaged.

And finally, exposing children in the elementary schoolroom will add to both the amount of electromagnetic radiation exposure and the accumulated length of exposure over their lifetime that they will be exposed. No one can argue that the children of today's generation will be exposed to far greater amounts of electromagnetic radiation and will be exposed to it for a much longer period of time than any generation before. We simply don't know the consequences of this increased and cumulative exposure. And it's an experiment that we shouldn't place our children in. Why set up these networks without understanding any of the long-term consequences? Did we not learn a lesson from the tobacco and asbestos industries?

Effects of WirelessRadio Frequency Radiation Although no studies have been done on Wi-Fi per se there is a generous amount of research that has been carried out on cell phones, cell phone towers and masts. Since the Wi-Fi signal is the same type of radiation (only the frequency is different) one can assume with reasonable assurance that the effects of exposure to Wi-Fi will follow the same pattern of exposure to cell phones and cell phone towers.

Here's an example of what can happen. Let's say one works in a schoolroom or office where wireless access, or Wi-Fi, is used. In other words, we are continually exposed to a constant bombardment of electromagnetic radiation waves. Over time, sitting or working in this classroom or office, the cells of the body gradually loose their energy and consequently their ability to communicate. What if the function of a particular group of cells was to maintain the integrity of the blood-brain barrier? The blood-brain barrier is an intricate membrane that keeps harmful substances and toxins from contacting sensitive brain tissue. But what if the cells of the blood-brain barrier can't communicate or don't work any longer? The barrier would break down and this would allow harmful substances to enter. Those substances would then come in contact with sensitive brain cells. The result would be injured and damaged brain cells. This is just one example of how a particular group of cells can be adversely affected by electromagnetic radiation. In fact, studies have shown that placing a call on cell phone for just two minutes can disable the blood-brain barrier. 2 The same case could be made for the immune system and any other major "system" of the body since different cellular groups perform different functions to keep us healthy.

There are more than a dozen studies linking an increased risk for brain cancer and acoustic neuroma (tumor of the auditory nerve) to radio frequency radiation from cell phones and cordless phones. 3

Even the World Health Organization (WHO) is concerned about the effects of radiofrequency radiation on children's health. In a recent WHO publication they wrote:

"The possible adverse health effects in children associated with radiofrequency fields have not been fully investigated."

"Because there are suggestions that RF(radio frequency) exposure may be more hazardous for the fetus and child due to their greater susceptibility, prudent avoidance is one approach to keeping children's exposure as low as possible."

"Further research is needed to clarify the potential risks of ELF-EMF and radiofrequency fields for children's health."

Neurobehavioral effects of inhabitants living near a cell phone tower base station have also been studied. The following neuropsychiatric complaints were reported: headache (23.5%), memory changes (28.2%), dizziness (18.8%), tremors (9.4%), depressive symptoms (21.7%), and sleep disturbances (23.5%). 4 In addition, tests of attention and short-term auditory memory were significantly lower in the exposed participants than in control groups.

Obviously, people living close to cell phone towers have an increased risk for developing neurobehavioral problems.

Will We Medicate Our Children Unnecessarily? If indeed neurobehavioral symptoms are produced by radio frequency radiation and these frequencies are continually emitted throughout our schools what might this suggest about the abnormal behavior of students in the classroom? Might parents be inclined and persuaded to medicate their children so that these undesirable symptoms can be controlled? If so, how many of these children would be medicated unnecessarily? Studies now show that the frequencies such as that emitted by cell phones cause abnormal brain hyperactivity. Such artificially induced hyperactivity would cause an unnecessary risk and expense to students who would be placed on some form of pharmaceutical intervention to aid in controlling these symptoms. Many of the drugs used in controlling hyperactivity, such as Ritalin, Concerta, and methylphenidate are in the amphetamine-like class of pharmaceuticals. What a tragedy it would be to find out years later that this form of medication was unnecessary and could have been avoided if we would have chosen precaution over convenience.

Learning Issues As discussed earlier, the mechanism of harm caused by electromagnetic frequencies occurs at the cellular level. The eventual outcome of this harm is disruption of cell-to-cell communication. When the disruption of cell communication occurs cells can't "talk" to each other. When cells can't communicate cognition is affected, the ability to learn is affected, the ability to retain information is affected, and behavioral problems can occur.

Makes Kids Susceptible To Other Stressors Radiofrequency radiation is also a stressor to the body. The mere fact that the cells of the body react to these frequencies as discussed earlier indicates that they are harmful. When the stress response occurs from exposure to electromagnetic frequencies the body responds by releasing stress proteins, also known as heat shock proteins, to minimize the ensuing damage. The release of heat shock proteins is just one stress response mechanism that has been identified. Other mechanisms include the triggering of adrenal hormones like adrenaline. Continual stress is not healthy as it can eventually fatigue the adrenal gland, suppress the immune system, and lead to fatigue causing difficulty in concentration. Sleep disturbances may also occur.

Immune System Affected Evidence also exists that radio frequencies produced by such devices as cell phones, Wi-Fi, computers, televisions, etc. can trigger skin reactions.5 Microwave frequencies can trigger the release of chemicals from mast cells. Mast cells in the skin will break open and release chemicals that cause the symptoms of allergic skin reactions. 6 One of the chemicals released by mast cells is histamine. Histamine is often responsible for the symptoms of allergies such as runny nose, watery eyes, inflammation and difficulty breathing. Histamine also constricts the airway leading to or worsening the symptoms of asthma. It is of interest to note that the rate of asthma in children has doubled since 1980 and asthma now affects one in 10 children. The cell phone was introduced in1983 and has seen explosive growth in use in the last decade. Could there be a correlation between the rising rates of asthma, an immune system problem, and the escalating use of cell phones and wireless technology? Certainly, one could anticipate that chronic exposure to these radio waves over time can lead to chronic inflammatory responses.

Electromagnetic Radiation Connected To Autism A recent study has now suggested a direct link between autism and electromagnetic radiation. It appears that EMR may accelerate autistic spectrum disorders. 7 It is noteworthy that the increasing rates of autism parallel the growth of the cell phone and wireless industry. This appears to occur as a result of the trapping of heavy metals within the cell and the inability of the body to excrete the toxic metals present that are often introduced into the body through vaccinations. Heavy metals are neurotoxic. When this excretory process is prohibited these heavy metals, such as mercury, lead, beryllium, and aluminum, damage nerve structures and interfere in inter-cellular communication. This leads to neurological problems and conditions like those found in autism spectrum disorders. This particular study has shown that when electromagnetic radiation is largely eliminated the efficiency of heavy metal detoxification and removal was dramatically increased. In other words, the body was able to excrete and eliminate heavy metals when it had not been able to do so previously. This leads to the suggestion that (1) we need to reduce or eliminate electromagnetic radiation from any child's environment and (2) measures need to be taken to repair the damage that has already been done by electromagnetic radiation. Although this study looked specifically at autism the same case could be made for attention-deficit disorders and related conditions.

Occupational Hazard For Teachers And School Staff Children will attend school in a particular building for a finite number of years and then move on. For a child the length of time spent in a particular building or location is predetermined. Therefore their exposure levels to this form of radiation will probably change. But what about the teachers and staff members who continue to work in the same building for many, many years? For these workers and teachers the exposure in their building from Wi-Fi networks and radio frequency radiation is continual. What are the effects of this exposure after years and years of time? Will teaching in a Wi-Fi enabled school become an occupational hazard like that of an electrician? These are questions that must and should be answered before, rather than after, any installation of radiation-generating equipment is placed in service.

Wi-Fi In European Schools The European Environment Agency is calling for immediate steps to be taken to reduce exposure to Wi-Fi, cell phones and cell phone towers and masts. Recent international scientific reviews have concluded that electromagnetic radiation safety limits are "thousands of times too lenient" and one official British report came to the conclusion that the development of cancer from cell phone use could not be ruled out.

Sir William Stewart, chairman of the Health Protection Agency in the UK, is calling for a formal investigation into the hazards of using wireless networks in schools. He's asking that students be monitored for health problems from the networks. Joining him in health concerns over Wi-Fi installations in schools, the Professional Association of Teachers are calling for the Secretary of State for Education in the UK to begin an official inquiry into the issue.

Recently, parents of children at an English school have won a major battle in getting a mast tower removed from their school. Parents indicated that both students and staff complained of symptoms such as insomnia, headaches and numbness. It seems 56 percent of children had trouble sleeping, 54 percent developed headaches and migraines, and 46 percent reported dizziness and numbness. 86 percent of staff members had problems sleeping, 59 percent reported headaches, and 95 percent of staff reported fatigue and numbness. Nosebleeds, nausea, and dizziness were also reported. 8

Dr. Gerd Oberfield, head of environmental health and medicine in the province of Salzburg, Austria, calls the installation of Wi-Fi "dangerous." In fact, the government in Salzburg has been advising schools not to install Wi-Fi for well over a year now and is considering a complete ban on Wi-Fi networks.

Stowe School in Great Britian recently removed its Wi-Fi equipment from its building. One of its schoolmasters who had taught there for 28 years developed headaches and nausea immediately after Wi-Fi was installed.

International Association of Fire Fighters In 2004, the International Association of Fire Fighters (IAFF) voiced its opinion on cell phone towers and antennas by opposing the installation of cell phone antennas on or near fire stations until a credible study can be done to establish their safety. In studying the available science the IAFF found over 49 references that led them to conclude that they should oppose the placement of cell phone antennas on fire stations. Some of the effects that have been documented by fire fighters include slowed reaction times, sleep deprivation, severe headaches, lack of focus, tremors, and vertigo. 9

What About Wi-Max The latest development in the world of digital communication is something called Wi-Max. Wi-Max is intended for use as a network for large metropolitan areas. Where Wi-Fi is limited to a range of about 100-300 feet, Wi-Max can provide broadband wireless access up to 30 miles from fixed base stations and 3-10 miles from mobile base stations. It's been described as Wi-Fi on steroids. It's used in much the same way as Wi-Fi and will soon become the standard for Internet access. Imagine the implications. Whole metropolitan cities blanketed with Wi-Max wireless coverage. How convenient and "connected" do we really need to be?

Conclusion We currently have no studies that are specific to Wi-Fi. However, when assessing the safety issue we can and should look at technologies that are similar and relevant to Wi-Fi to draw our conclusions. This would seem appropriate since Wi-Fi operates in the same manner as other more heavily studies similar technology and the basic mechanism of harm from all wireless technology is the same.

There are countless reports and studies raising caution signals about the effects on human health from exposure to cell phone radiation, cell phone towers, Wi-Fi, and wireless technology in general. The fact remains that wireless technology is a potential carcinogen. So was tobacco. So was asbestos. So were X-Rays. Like these other hazards, which were all at one time only "potential carcinogens," wireless technology needs further study before we decide to randomly subject ourselves and our children to the potential harmful effects it seems to cause. How long will we wait for these studies? Another 20 years or more? How many lives will be adversely affected or lost while we take the wait-and-see approach?

What can you do? Don't let your children use a cell phone. Don't live near a cell phone tower. Don't use wireless Internet connections or cordless phones in your home. Provide good nutrition to your children in the form of lots of fruits and vegetables. Everyone needs lots of antioxidants to protect themselves from the free radicals being produced by these high levels of radiation. Good quality water is a must, too.

Get involved in your child's school. Get on the school board. Ask questions regarding the use of Wi-Fi in the school. Object to the installation of such equipment if and when the possibility is discussed.

School districts today are under ever-increasing financial pressures. Healthy lease money is being provided by the wireless industry to install cell phone antennas on school buildings. Once again, this is an unneeded and unnecessary exposure risk for our young people. Does the extra income provided by the wireless industry outweigh the potential risk to our children? The studies say no and we as parents and responsible citizens need to convey that message to our school boards and legislators.

Two-time Nobel Prize nominee, Dr. Gerald Hyland, a physicist, had this to say about cell phone towers. "Existing safety guidelines for cell phone towers are completely inadequate. Quite justifiably, the public remains skeptical of attempts by government and industry to reassure them that all is well, particularly given the unethical way in which they often operate symbiotically so as to promote their own vested interests."

Reliance Leading the WiMAX Charge in India

The Indian Broadband market is expected to expand almost exponentially over the next five to six years according to a report published recently and it would appear that the use of WiMAX (short for World Interoperability for Microwave Access) is leading the charge with usage expecting to rise to over 21 million users by 2014. WiMAX where installed correctly is designed to provide greater efficiency, development and utilisation of broadband services.

This echoes further additional reports that confirm that the Indian economy is flourishing and the demand for telecommunications networks and services has finally outpaced the availability provided for by what are euphemistically described as conventional legacy wired telecommunications.

It would appear that within the Indian marketplace that vendors, operators and system integrators are all coming together to engineer a bandwidth revolution, the like of which has never been seen before.

Leading the charge in this particular telecommunications sub sector would appear to be Reliance Technology Ventures; the VC (Venture Capital) subsidiary of Mumbai based Reliance AD Group.

One of reliance technology ventures sister companies reliance communications is at present one of India's largest CDMA (code division multiple access) suppliers and is now serving its intention to move into the GSM marketplace.

It has achieved this by its recent funding of a large undisclosed investment in E-Band, a San Diego based manufacturer and designer of multigigabit wireless communications systems.

Given the current rate of growth within the Indian marketplace industry experts are predicting with current levels of investment and expansion we may be at the beginning of what could possibly be one of the world's top three WiMAX marketplaces.

At the forefront of this expansion have been major carriers such as Reliance Technologies who are already running commercial WiMAX services in Bangalore. Should these initial tests prove to be successful and if you want to go on initial criteria and that would certainly be the case, they are predicting that by 2014 the accumulated WiMAX subscriber base in India alone will reach 21 million.

Partly because of its rapid expansion equipment costs the general market costs are dropping whilst revenues are rising. Costs in India are being driven down faster than in any of the major worldwide marketplace.

At present industry analysts state the penetration of broadband throughout India at present lies at an extremely low figure of .2%. With the new technologies and investment rapidly being made available for the industry, experts are predicting the market to double within the next couple of years.

It cannot be denied that globally, investment in emerging wireless technology services such as WiMAX is growing certainly more than any other similar mobile technology.

It is one of those things that you can get a rough estimation of how mature technology marketplace is when you sit back and analyze the number of hardware equipment manufacturers who are prepared to "jump in with both feet," desperate to claim vital market share.

Elsewhere in Asia, WiMAX is expanding and it would appear that from other marketplaces, certain Asian telephone companies are planning to run controlled tests of these services based on WiMAX technology in the United Kingdom next year.

Certainly it would appear that the initial WiMAX tests run by Reliance WiMAX in Bangalore are going well and that the costs of the Reliance Data Card are expected to drop accordingly.

WiMAx VS Wifi

WiMax (802.16) is is a newer standard of wireless networking designed to provide the last mile of high speed internet access to the end user. Some people would call Wimax WiFi on steroids but this would be to broad of an assessment. Wifi was and still will be used in LAN environments for the foreseeable future. WiMax was designed to provide (MAN) Metropolitan Area Access, to homes and businesses.

WiMax base stations will have the ability to provide approximately 60 businesses with T1 access and hundreds of homes with DSL/Cable speed access…in theory. Engineers are stating that WiMax has the capability of reaching 30 Miles but real world testing has shown 4-8 mile working radius.

WiMax (MAN) deployments are similar to a WiFi network. First the ISP would have their T3 or higher access. The ISP would then use line of sight antennas (Bridges) to connect to towers that would distribute the non line of sight signal to (MAN) residential/business clients.

WiMax line of sight antennas operate at a higher Frequency up to 60mhz. Distribution antennas do not have to be in the line of sight with their clients. Non – line of sight towers operate on a range similar to WiFi . WiMax can operate right next to cell phone towers with no interference.

WiMax networks are similar to Wifi in deployment. The Wimax Base station/Tower will beam a signal to a WiMax Receiver. Similar to a WiFi access point sending a signal to a laptop. As far as I can tell laptops will be shipping with Wimax receivers in 2006.

QOS (Quality of Service) is an major issue with WiMax because of the number of people accessing a tower at once. Some would think that a tower could be easily overloaded with a lot of people accessing it at once. Built into the WiMax standard is an algorithm that when the tower/base station is nearing capacity then it automatically will transfer the user to another WiMax tower or cell. Unlike a Wifi clients who have to kind of fight to stay associated with a given access point; WiMax will only have to perform this hand shake at the MAC level the first time they access the network.

WiMax is designed for building a network infrastructure when the environment or distance is not favorable to a wired network. Also, WiMax is a cheaper and quicker alternative than having to lay wire. Third world countries will greatly benefit from deploying WiMax networks. WiMax can handle virtually all the same protocols Wifi can including VOIP. African countries are now going to start deploying WiMax networks instead of cell phone networks. Disaster zones can also utilize WiMax giving them the ability to distribute crisis information quickly and cheaply.

Militaries are already using wireless technology to connect remote sites. Logistics will be simplified with the ease of tracking with RF technologies. WiMax can also handle Webcams and streaming video which would give commanders eyes on target capability. Just imagine if planes were able to drop preconfigured self deploying WiMax antennas in strategic areas giving troops real time battlefield intel. Armed with wireless cameras, drones and a GPS one soldier would truly be an Army of One.

As WiMax is deployed in more areas theory and real life capabilities of WiMax will come to light. The differences between WiMax and Wifi are simple. Think of a WiMax network as an ISP with out wires, with the signal providing your internet access to your business/ home. Wifi will be used within in your LAN for the near future.

Uses of WiMAX

WiMAX is designed as a wireless alternative to DSL and cable for last mile broadband access and as way to interconnect Wi-Fi hotspots into a Metropolitan Area Network. Although, the actual uses for WiMAX overlaps those for Wireless Local Area Network up until the mobile Wide Area Network level. Telephone and cable companies are closely probing the potential of WiMAX as a "last mile" connectivity option. This will result to a better-priced service for both home and business customers and not to mention the elimination of the "captive" customer bases for both telephone and cable networks.

In theory, WiMAX can provide connectivity to users within a 31 mile radius even if there is no direct line if sight. However, actual field tests show that the practical limits seem to be just around 3 to 5 miles. According to WiMAX proponents, the technology can provide shared data rates up to 70 Mbit/s. This is enough to connect 60 T1-type connections simultaneously and over a thousand homes running at 1 Mbit/s DSL level connectivity. Practical maximum data rates in actual field tests show can only go between 500 kbit/s to 2 Mbit/s and is quite dependent on the conditions at a given site.

Despite the numbers given, there are a lot of ways to improve the speed and range of a WiMAX connection using pre-existing technology. One interesting option for companies with analog cellular network is to let WiMAX "share" a cell tower since it will not interfere with any of the function of the cellular arrays while utilizing the licensed radio frequencies of the analog cellular network to increase its speed and range. A WiMAX antenna can also be directly connected to an Internet backbone using a fiber optic cable. This is one of the means to increase bandwidth for data-intensive applications running across a wireless network or as a back-haul for cellular phone and Internet traffic from a remote area back to a backbone. WiMAX can effectively improve a wireless infrastructure in a decentralized, inexpensive and deployment-friendly manner.

WiMAX is seen as a very good alternative to expensive urban deployments of T1 back-hauls in developing countries with limited wired infrastructure and cruel geography. The cost to install a WiMAX station as a single hub or using an existing cellular tower will be very small compared to a wired solution. WiMAX's 31-mile diametrical range also works well with the low population density and the wide flat areas common to developing countries. Some areas have skipped wired structures due to inhibitive costs and WiMAX can easily fill the gap in-between with its low-cost wireless solution.

There is no global license assigned for WiMAX although it has a very wide RF spectrum under the IEEE 802.16 specifications. The primary band used in the US for WiMAX is around 2.5 GHz although majority of the band is already assigned to Sprint Nextel. In other parts of the world, the bands used are usually around 2.3/2.5 GHz, 3.5 GHz and 5 GHz where the 2.3/2.5 GHz is widely used in Asia.

The World of WiMAX

You might start asking, "What is WiMAX anyway and what can I get from it?" Well, if you're the type of person that travels a lot to remote areas and is always in a dire need of Hi-speed Internet access, then WiMAX is for you. WiMAX stands for Worldwide Interoperability for Microwave Access. It is also known as IEEE 802.16 and by the term WirelessMAN (Wireless Metropolitan Area Network).

A group known as the WiMAX Forum was formed in April 2001 to oversee and promote the interoperability and conformance of the said standard. The WiMAX Forum is the only organization exclusively devoted to certify the Broadband Wireless Access products and makes sure that different vendor systems work effortlessly with one another. All those who pass the interoperability and conformance test acquire the "WiMAX Forum Certified" mark on their products and are allowed to put the mark on their marketing materials. The Forum also warned that some manufacturers stating that their product is "WiMAX-ready" or "WiMAX-compliant" are not "WiMAX Forum Certified".

In principle, WiMAX is very different to Wi-Fi. The media access controller of Wi-Fi is using contention access where all subscriber stations that intend to pass data to the access point are competing for the access point's attention on an arbitrary basis. This significantly reduces the throughput of the nodes as their distance to the access point increases since closer nodes tend to repeatedly interrupt their transmission. This makes VOIP and IPTV service very difficult to implement and maintain using Wi-Fi especially when there are a significant number of users involved. The WiMAX media access controller uses a different approach. A WiMAX subscriber station needs only to compete once and this only happens during the initial entry to the network. The base station then assigns a time slot and other subscriber stations are not allowed to transmit during that time slot and wait for their turn. The time slot can enlarge or constrict; yet it still remains assigned to the subscriber station. The scheduling algorithm used by the WiMAX base station can handle overload with ease and remains stable. This makes WiMAX very efficient.

The original WiMAX standard uses the 10 to 66 GHz range and in 2004, added the 2 to 11 GHz range. Most parts of the additional frequency range are already unlicensed internationally although a few still need domestic licenses. WiMAX also uses a relatively stronger encryption algorithm since this was a major concern after the initial Wi-Fi implementation. WiMAX also aims to come up of a solution for nodes without any direct line of sight. The 5-6 Ghz spectrum is considered to be the most reasonable range that can provide the optimum performance and cost effectiveness for point to multi point deployments. The details on the implementations and performance of WiMAX in non-line of sight situations are still unclear since it is still in the experimental stage. Recent development of WiMAX includes full mesh networking capability where a WiMAX node acts as a base station and a subscriber station at the same time.