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New Wi-Fi coming in waves, but surf at your own risk

David Callisch, VP of marketing, Ruckus Wireless | June 24, 2013
802.11ac promises to deliver the next big step in performance, but without better RF controls performance boosts will be limited.


And many vendors won't tell you that the modulation techniques that allow faster communications will only benefit clients at close range with a very high signal-to-noise ratio (that the preponderance of enterprise access points can't deliver). Range will also be an issue as 5GHz Wi-Fi signals have shorter useful range and do not penetrate obstructions as well as 2.4GHz signals.

As a result, it's important to look for 802.11ac products that focus RF signals, increasing gain and extending reach to enable higher data and modulation rates. The ability for Wi-Fi systems to adapt to changing environmental conditions and a myriad of different client types significantly increases the likelihood that all these capabilities (that make 802.11ac so attractive to enterprises) can actually be put to good use.

Finally, keep in mind that 802.11ac will come at a cost -- a higher cost. This cost is not only for the access points but also for new Power over Ethernet switches that will have to support the higher-power 802.3at standard that many of these new 802.11ac APs will require.

Signal path control adds big value to 802.11ac
For 802.11ac to work as advertised, it's essential to have greater control over the signal paths within the RF spectrum.

This proved to be the case as the industry moved from 802.11g to 802.11n, which introduced multiple Wi-Fi radio chains (MIMO), a whole bunch of new PHY rates, spatial multiplexing and the aggregation of frames. The same is true as companies migrate from 802.11n to 802.11ac.

For instance, with per-packet adaptive antenna control, polarization diversity, and active channel selection techniques, Smarter Wi-Fi APs maximize the potential of 256-QAM with 802.11. This means:

  • Greater SNR/SINR increases the useful downlink range of 256-QAM
  • Adaptive polarization diversity with maximal ratio combining (PD-MRC) and higher uplink receive sensitivity increase uplink range of 256-QAM
  • APs that can select channels with more capacity and less noise and interference


Also with the possibility of 20MHz, 40 MHz, 80MHz or 160MHz channel widths, it becomes increasingly difficult to determine what channel widths are optimal for each environment based on spectral reuse, the number of APs, transmit power, client device types and channel support, etc.

Predictive channel selection tackles these problems by determining the highest-capacity channel available by using statistical modeling of actual traffic over time. Predictive channel selection helps 802.11ac to:

  • Learn the channels best suited for bonding at any given time
  • Adaptively change channel as environmental conditions fluctuate
  • Discover the best channel settings for the environment, the client device types and count, channel width support, and the amount of traffic at each bandwidth setting

Finally, when multi-user MIMO comes around, it will be imperative to have access points that can direct Wi-Fi signals to each client to better separate signals. This enables higher sustained data rates, and increased client capacities can be achieved because users can get on and off the Wi-Fi network faster and with less packet loss and retransmissions.


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