Wireless networking using the unlicensed and (licensed) 5GHz frequency bands is the new kid on the block. It uses the same basic technology and methods as 802.11g (54Mbps) wireless but operating in the 5.1-5.8GHz frequency bands instead of the 2.4GHz band. Also, unlike 802.11g, it uses OFDM technology over the whole speed range (1-54Mbps); 11g only uses OFDM at speeds above 20Mbps.
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Factors affecting Wireless Transmission
Multi path effects
All wireless signals suffer from an effect called Multi-path effects. These can be explained as coherent signals (signals from the same source) arriving at the antenna at different times due to the difference in path length. Several signals from the same source meeting at the receiving antenna can arrive in phase, out of phase or in between depending upon whether the signals have come direct or by reflection.
When the level of each incoming signal is included, the effects can be any of the following:
|Equal||Out||Possible loss of reception|
The conductivity of the reflector and polarisation of the wave before reflection primarily affect the level of the signal. Horizontal polarised signals, which are parallel to the reflecting surface, will reflect almost totally without appreciable loss at the point of bounce.
Vertically polarised signals are perpendicular to the reflecting surface, and will either be totally reflected from a conductor, or will propagate along the surface (depending on the angle of the arriving energy). Since radiated waves penetrate lossy materials, energy can be lost to heat generation. Continue reading…
In less than a decade, wireless LANs have evolved from an innovative idea to an indispensable technology for millions of business and consumers. This technology will continued to evolve. The latest generation of high-speed wireless LAN solutions, based on the IEEE Draft 802.11n standard, are now available.