Understanding 802.11b & 802.11g (WiFi) Range

If your problem is the wireless range of your laptop or desktop then read this and follow the steps below. Wireless networking (WiFi) at 2.4 GHz is a two-way system. Each device must be capable of both sending and receiving a signal equal distances. Think of it as two people, a substantial distance apart, throwing a ball to each other. Person A has to be strong enough to throw the ball, that substantial distance, to person B. Person B also has to be strong enough to throw the ball back, that substantial distance, to person A. If neither Person A nor B can throw the ball that distance they will not have much of a throwing game. Access points and wireless routers (as shipped from the manufacturer) 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 (factory) antennas that came with your card.   Access Point To Client-side Device (WLAN/PCI Adapter Card) Output power of client-side devices with factory antennas are less than that of access points. A signal from an access point will travel farther than that of the client-side device. A high-gain antenna solution extends the range of the client-side device, increasing its power closer to that of the access point. (solution dependent on specific situation variables) Please note that extending the range of your wireless 802.11b or 802.11g wireless device is only a piece of the whole puzzle. At 2.4GHz (the frequency that 802.11b and 802.11g WiFi operates at), Line-Of-Sight can be an important factor. Please see below regarding Line-Of-Sight.   Step 1: The Desktop Fix: Replace the antenna and desktop card with the D-Link Solution.   Step 2: The Laptop Fix: Most laptop cards have very poor receive sensitivity and therefore have very limited range. Replace your laptop card with a better card and consider additional antennas for those cards that have external antenna connectors if your range is greater than 75 - 100 feet.

Understanding The Importance Of Unobstructed Line-Of-Sight With WiFi

Defining Line-Of-Sight 802.11b and 802.11g at 2.4GHz (equipped with and using a vertically (or linear)-polarized antenna) requires unobstructed visual Line-Of-Sight (LoS). Unobstructed Line-Of-Sight means just that; there should not be trees, terrain, buildings, or structures between your two (antenna) points. Basically both antennas should physically see each other in an external outdoor bridge. The radio waves at this low frequency will not penetrate metal, steel, concrete, cement, stone, brick, etc. very well, if at all. For interior applications, dry wall, sheet rock, and wood shouldn't be a problem. Surrounding the visual Line-Of-Sight is the Fresnel zone (image 1). Any obstructions that come into the Fresnel zone, although not obstructing the visual Line-Of-Sight, may also slow down, hinder and effect your signal. The radio waves may deflect off of those obstructions. This is called Near Line-Of-Sight (nLoS, image 2). Although you may see a slight signal with nLoS situations, your data transfer rate may decrease. You may find you are incapable of accessing the Internet. 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 (NLoS, image 3). Any signal, in this case, will be minimal or non-existent. click diagram to enlarge   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. Please note that tree branches that cross the visual Line-Of-Sight will move with the wind. This movement will disrupt and have an effect on a vertically-polarized WiFi signal. Keep in mind, if you are conducting your site survey during late Fall and Winter months, those trees will fill in come Spring and Summer. Additionally, weather, RF interferences, and other site variables can have an effect on your signal too. Linear (Vertically) -Polarized vs. Multi-Polarized vs. Circular-Polarized Most WiFi, 802.11b and 802.11g, antennas on the market today are linear (or vertically) -polarized. This includes the small, "rubber ducky" antennas that ship from the factory with most wireless devices. A radio wave travels through the air about the size of a pine needle. If the antenna is vertically polarized the pine needle must remain vertical, as sent. If the signal hits an obstruction the signal will flip or rotate into multiple positions as it gets to the receiving radio's antenna where it will be seen as noise. The vertically-polarized antenna will not capture that signal. A multi-polarized antenna, one that sees rotating signal on all polarizations, will succeed at capturing that signal. Please see our WiFi-Plus line of multi-polarized, tree-penetrating antennas for these applications. In a circularly-polarized antenna, the plane of polarization rotates in a corkscrew pattern making one complete revolution during each wavelength. A circularly-polarized wave radiates energy in the horizontal, vertical planes as well as every plane in between. If the rotation is clockwise looking in the direction of propagation, the sense is called right-hand-circular (RHC). If the rotation is counterclockwise, the sense is called left-hand-circular (LHC). Please see our Luxul line of circular-polarized antennas.