Ruckus Wireless Clears the Air on Wi-Fi's Biggest Enemy: Interference

SUNNYVALE, Calif., May 3 /PRNewswire/ -- Ruckus Wireless™ today applauded Cisco Systems for validating the need to confront one of Wi-Fi's biggest problems: interference.

In concert with Cisco's recent CleanAir announcement, Ruckus Wireless outlined advances in RF management technologies that go beyond mere discovery of interfering objects and conventional interference mitigation techniques involving disruptive, WLAN-wide channel and power adjustments.

Ruckus' patented smart antenna arrays coupled with dynamic beamforming intelligence enables a Wi-Fi access point (AP) to automatically detect and steer transmissions away from noisy signal paths.   Interference is thwarted at the point of detection without interrupting client connections on the AP.

To further detail these techniques, Ruckus will be hosting a free technical Webinar on "Avoiding RF Interference" on Wednesday, May 26th at 10 a.m. PDT (register here: http://tinyurl.com/2dbs3v8).

"Wi-Fi is proliferating at an accelerated pace with new Wi-Fi enabled devices hitting the market every day. Interference in the unlicensed spectrum is rising quickly on IT managers' agendas. Cisco has clearly recognized this," said Steve Martin, VP of Engineering for Ruckus Wireless.

"However, Cisco's approach, like others before it, simply camouflages the problem. Wi-Fi access points using conventional antenna systems are fundamentally incapable of adapting to a changing RF environment," said Martin. "Without explicit, dynamic control over how and where RF energy is transmitted, there is no way to respond to real time interference even as it is detected.  Our patented Smart Wi-Fi technologies effectively mitigate interference by automatically rejecting radio noise and steering Wi-Fi transmissions to the best signal path on-the-fly."

Martin noted that ironically, the biggest source of WLAN interference often stems from enterprises' own Wi-Fi networks. "Co-channel interference from adjacent access points is the primary culprit of wireless performance problems facing companies today. And it's only getting worse."

Understanding Wi-Fi Interference and Coping with It

A major problem for Wi-Fi networks which operate in the unregulated band, interference is the presence of unwanted RF signals (i.e., noise), that disrupt normal system operations. Legitimate transmissions may be received incorrectly in the presence of interference. When an 802.11 device hears a signal, whether it is a Wi-Fi signal or not, it will defer transmission until the signal ceases.  Hence RF noise can also bring an AP to a standstill.  

Traditional Wi-Fi APs use omni-directional antennas that waste energy, create interference for adjacent APs and offer little control over transmissions because omni-antennas radiate energy in all directions indiscriminately.  

To maximize the Signal to Noise Ratio (SNR), "optimized" or "smart" APs employ high gain antennas or high power amplifiers. This often makes interference problems worse at a macro level and can result in other undesirable side effects such as causing mobile clients to remain associated to an AP long after they should have roamed to an AP in closer proximity.

A conventional technique for dealing with interference in a WLAN involves changing to a "cleaner" frequency channel.  Channel changing by an AP requires its connected clients to disassociate and re-associate.  This causes disruption to voice and video applications.  Furthermore, it can have a domino effect as neighboring APs have to change their channels as well to avoid co-channel interference.  A wide-spread channel adjustment throughout a WLAN may necessitate a site survey and manual tuning.  

In reality, channel changing is often impractical.  The vast majority of Wi-Fi devices today use the 2.4 GHz frequency band which offers only three non-overlapping channels. Even with the 5GHz band there are only 11 non-overlapping 40MHz channels available, not to mention the numerous non-Wi-Fi interferers such as microwaves, cordless phones, and video surveillance cameras that hop between multiple frequencies.    

"Switching channels should be a solution of last resort. It is fundamentally better for the macro network if access points can automatically direct Wi-Fi transmission over paths that are known to be free of RF noise," said Martin. "While detecting and identifying Wi-Fi interference has been possible for years with a range of low-cost spectrum analyzers, until recently, the ability for Wi-Fi access points to proactively reject and mitigate interference in real time has eluded the industry."

Smarter Wi-Fi to the Rescue

Unlike other Wi-Fi systems, Ruckus Wireless APs integrate patented intelligent antenna array and dynamic adaptation technologies that form and direct Wi-Fi transmissions over the best available signal path in real time.  

Known as BeamFlex™, this technology provides up to 10dB of signal gain thereby reducing the number of APs required for any given coverage while increasing the stability of client connections at long distances and challenging locations. BeamFlex also delivers up to 17dB of interference rejection, which plays a critical role in sustaining WLAN reliability and consistent performance.

Also, the self-learning, self-optimizing BeamFlex adaptation algorithm selects the optimum antenna combination to steer each packet over the best path. Learning from the feedback packets inherent in the 802.11 protocol, BeamFlex determines if the best performance is being achieved for each client at any given time.  If performance to a client begins to degrade due to interference, obstacles or other environmental conditions, BeamFlex immediately adapts to the current optimum antenna combination, thereby avoiding problem signal paths to ensure the highest performance possible.

"Interference is better dealt with at the AP without disrupting the rest of the WLAN. Our systems take active control of signal steering to diminish the impact of interference without human intervention while taking into consideration the impact on the client," said Martin.  In contrast to conventional Wi-Fi technology, Ruckus BeamFlex (Smart Wi-Fi):

• Automatically avoids Wi-Fi interference through active interference rejection,
• Continuously calculates and tracks the best signal path for all clients based on implicit feedback from each client,
• Uniquely focuses Wi-Fi signals only where they are needed,
• Provides up to 10dB of signal gain and 17dB of interference rejection,
• Eliminates manual tuning or site surveys necessitated by constant channel changes,
• Offers over 4,000 different antenna combinations that can be used to steer each packet transmission for ultra-reliability and performance, and
• Delivers a two-to-four fold extension of signal range.

SOURCE Ruckus Wireless