Wireless Communication Protocols

Topics: IEEE 802.11, Orthogonal frequency-division multiplexing, Multiplexing Pages: 2 (783 words) Published: April 17, 2008
Wireless communication protocols have evolved rapidly since the introduction of 802.11 Legacy over a decade ago. Over the last 10 years we have seen efficiency and performance increases on all fronts, which have lead to greater range and faster transfer speeds. With Legacy 802.11 protocols, speeds maxed out at around 2 Mbits/sec and indoor range was only about 20 meters. In 1999, the 802.11 protocol got a couple of amendments in the form of 802.11a and 802.11b. Both offered higher speeds and slightly greater range, but there were many differences between the two standards in how they achieved those two things. 802.11b uses an offshoot of the same modulation technique as the older Legacy protocol, known as complementary code keying (CCK) (based on direct-sequence spread spectrum used in Legacy). Both protocols also use CSMA/CA for multiple access, which is the reason both Legacy and 802.11b protocols were much slower than any of the other versions we’ve seen – CSMA/CA carries a lot of overhead meaning much wasted bandwidth. With 802.11a, we see much faster speeds (54Mbits/sec versus 11Mbits/sec with 802.11b) thanks mostly to orthogonal frequency-division multiplexing (OFDM) and its use of the 5MHz bandwidth spectrum which is much less crowded than the 2.4GHz spectrum used by 802.11a and Legacy protocols. Despite these distinct advantages, 802.11a lagged behind 802.11b due to slow availability of the 5GHz hardware to manufacturers and the fact that first wave of hardware put on the market was plagued with bad performance. By the time the second wave of hardware was available, 802.11b had so many users that it didn’t make sense to switch for most users who had just finished stabilizing their networks. The next protocol to hit was 802.11g, which the IEEE ratified in 2003. 802.11b users were starving for faster speeds by this time, but due to compatibility issues, had not switched to 802.11a which had a much smaller hardware base. 802.11g was the answer to all of...
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