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Toward a Gigabit Wi-Fi Nirvana: 802.11ac and 802.11ad

By Matthew Gast, director of product management, Aerohive Networks, special to Network World
February 14, 2011 05:04 PM ET

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802.11ad has the same gigabit goal, but is intended for use with new spectrum around 60 GHz to use. Range will be shorter, but the spectrum is "cleaner" because many fewer devices use it today. The open spectral band is large enough that the current 802.11ad draft supports nearly 7 Gbps throughput.

The higher data rates of 802.11ac and 802.11ad will have far-reaching influences into other areas of the protocol. CCMP, the existing encryption protocol first standardized in 802.11i, requires two AES encryption operations for every 16 bytes of data. To encrypt a 1,500-byte frame requires roughly 200 AES encryption operations. To make matters worse, CCMP is based on a "chained" mode of operation that requires in-order processing of the 16-byte chunks because chained cryptographic modes require the output of one stage to be used as the input to the next. Many engineers within the 802.11 working group expect that the high data rates of 802.11ac and 802.11ad will be too high for CCMP.

Fortunately, a solution is readily available in the form of the Galois/Counter Mode Protocol (GCMP), which has been incorporated into the 802.11ad draft. GCMP uses the same AES cryptographic engine, but embeds it into a more efficient framework. Compared with CCMP, GCMP requires only half the number of encryption operations, and, more importantly, is not chained so that GCMP cryptographic acceleration can be applied to an entire transmitted frame in parallel. The downside of the adoption of GCMP is that it is a new protocol and will only become available in new radio chips that support it, and an entire generation of centralized cryptographic equipment, such as the security processors in WLAN controllers, will become obsolete.

As with every jump in speed that has occurred in Wi-Fi, 802.11ac and 802.11ad present challenges for the network administrator. The move to gigabit Wi-Fi is needed to keep up with demand for Wi-Fi network capacity and enable Wi-Fi to remain the technology of choice at the edge.

Aerohive Networks is the leader in fully distributed, intelligent Wi-Fi systems.

Read more about lans & wans in Network World's LANs & WANs section.

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