WiFi networks (802.11) are being implemented to improve productivity, add convenience, and decrease costs. There will soon be new options. AT&T is currently launching WiMax service in major cities in the U.S. New satellite service from EutelSat in Europe, and ViaSat in the U.S., will provide additional options.

If there is high network utilization, today’s wireless LAN products can behave unpredictably. There is a large bandwidth available (83.5 MHz), but even so, the 2.4Ghz frequency band can sometimes become crowded with other 2.4Ghz devices like Bluetooth, microwave ovens, and cordless phones. However, currently, most enterprise WiFi networks have relatively low utilization. In the future, as wireless LANs assume a more central role, interference problems could become more critical.

Key Attributes

• High Data Rates.
• 802.11b: 11 Mbps, uses direct sequence spread spectrum (DSSS) modulation with Complementary Code Keying (CCK).
• 802.11g, 54 Mbps, uses orthogonal frequency-division multiplexing (OFDM) modulation to increase the throughput.
• 802.11g systems operate in the same 2.4GHz spectrum as the 802.11b systems and is backward compatible with existing 11b infrastructure. The term used to describe these devices is dual-band. Like 802.11b, 802.11g is limited to three non-overlapping channels.
• Reasonably priced.
• Weather Tolerant.
• Line of Sight is required for longer ranges (more than 1/4 mile).
• Maximum Wattage for the Transmitter (without FCC licensing) is 1 Watt.
• Half-Duplex Protocol: the system receives or transmits, but not simultaneously.

Access points and wireless routers 4G LTE WiFi Router Australia have an advantage over laptop and desktop cards because they have a higher output power and therefore have the ability to send a signal further then most laptop and desktop cards. When a higher-gain antenna is installed on a desktop card the output power of that device is now increased closer to the output level of the access point or wireless router therefore equaling the two devices. In some cases, the antennas of both the access point/wireless router and the desktop/laptop card may need to be replaced. This is if the distance you are attempting to achieve is greater than the capabilities of the access point/wireless router when using the antennas that came with your card.

Wireless network cards come in a couple of flavors, including a PCI card for workstations and PC cards for laptops and other mobile devices. They can act in a decentralized client-to-client mode, or in a centralized client-to-access point mode. An access point is essentially a hub that gives wireless clients the ability to attach to the wired LAN backbone. In a decentralized mode, the wireless network card is configured to talk with other wireless network access cards that are within its range. Decentralized client-to-client (also know as peer-to-peer) WLANs are useful for small roaming workgroups that do not require access to the LAN backbone. The plug and play capabilities of most wireless network cards make setup easy.

The use of more than one access point in a given area is facilitated by the use of cell structures, which are similar to what mobile phone providers use to maintain your coverage area. One of the benefits to roaming mobile users is the ability for one access point to automatically hand off communication to the next access point in a roaming cell.

When connecting two or more buildings it is best to first establish a wireless bridge between the two points in the backbone. If you want to be wireless within a building, once the building-to-building bridge is created, then attempt to establish a wireless network within each building or location. Desktops, laptops, and other client devices will not work reliably if the access point/wireless router is not resident in the building where the access point/wireless router is located.

Unobstructed Line-Of-Sight

802.11b and 802.11g at 2.4GHz requires unobstructed visual Line-Of-Sight (LoS). There should not be trees, terrain, or structures between your two (antenna) points. Radio waves at this frequency will not penetrate metal, steel, concrete, stone, etc. However, dry wall, sheet rock, and wood usually are not a problem.

Surrounding the visual Line-Of-Sight is the “Fresnel zone”. Any obstructions that come into the Fresnel zone, although not obstructing the visual Line-Of-Sight, may also slow down, hinder and affect your signal. The radio waves may deflect off of those obstructions. This is called Near Line-Of-Sight. Although you may see a slight signal with nLoS situations, your data transfer rate may decrease. An obstruction that cuts across the visual Line-Of-Sight and prohibits an optical visual between the two antennas in your bridge is considered Non-Line-Of-Sight.

You may find in your bridge application that the two antennas can visually see each other through spaces and breaks in an obstructing tree or tree line. Additionally, weather, RF interferences, and other site variables can have an effect on your signal too.

Security

Extensible Authentication Protocol, or EAP, is a universal authentication framework frequently used in wireless networks and Point-to-Point connections. EAP can provide a secure authentication mechanism between the client and NAS. EAP can support multiple authentication mechanisms, such as token cards, smart cards, passwords, and public key encryption authentication.