Beamforming: Ruckus Wireless applauds Cisco

SUNNYVALE, USA & BANGALORE, INDIA: Ruckus Wireless applauded Cisco Systems for validating the value of beamforming in improving Wi-Fi performance and outlined further systems enhancements, beyond implementing beamforming chips, that are essential to realizing the performance and reliability expected from next generation 802.11n technology.

Beamforming, typically implemented using on-chip digital signal processors, is an optional part of the 802.11n standard and as such, is not currently implemented in commercial client chips.

“Achieving adequate signal gain and coverage from transmit beamforming requires a number of systems-level complements, not the least of which is feedback from receiving clients and agile control of the signal beams over real time interference,”said Sudarshan Boosupalli, General Manager India at Ruckus Wireless. “Simply implementing a beamforming chipset without systems level optimization is like having a sports car driven by a robot, it works until another car swerves in front of it.”

Ruckus Wireless has introduced a beamforming system utilizing smart antenna arrays at the physical layer and intelligent antenna control software that adapt the antennas to optimize systems performance in an ever-changing RF environment. Compatible with, but without having to rely on silicon vendors for client feedback, the Ruckus-patented BeamFlex Smart Wi-Fi antenna system is the first-of-its-kind to use real time client feedback inherent to the 802.11a/b/g/n media access control (MAC) layer protocol to continuously optimize performance.

In addition, the Ruckus beamforming antenna arrays, composed of many directional antenna elements, are configurable in real time without human intervention to give access points complete control over the direction and form of Wi-Fi signals along with the ability to actively avoid and reject interference. With these controls, Ruckus Smart Wi-Fi access points can deliver three times the signal coverage while ensuring more consistent performance over conventional access points.

What is Beamforming?
Beamforming is a general signal processing technique used to control the directionality of the transmission and reception of radio signals.  An optional part of the Wi-Fi 802.11n standard, beamforming is defined in two basic types: implicit and explicit.

Implicit beamforming is designed to improve the transmission performance of a Wi-Fi access point by relying on mathematical calculations to determine how best to form Wi-Fi signals or beams toward receiving clients. But without explicit client feedback, access points have no way of knowing if the beams are optimum or if they are even working properly.

Explicit beamforming uses detailed channel matrix feedback from the client. However today’s Wi-Fi clients don’t support this 802.11n optional feature.

Beamforming using chips isn’t enough
“What vendors neglect to mention is the ‘either-or’ nature of all the 802.11n techniques that boost performance at the chip level. Using only two Wi-Fi radios to transmit, vendors can perform only one of 802.11n’s advanced techniques such as spatial multiplexing, transmit diversity or beamforming at any given time,” said Sudarshan Boosupalli, General Manager, Ruckus Wireless India. “The limitation severely degrades potential system gains.”

Sudarshan  noted that with only two antennas used to transmit Wi-Fi signals, as with Cisco’s newly announced 802.11n access point, the theoretical signal gain with beamforming is limited to 3dB.  This is the same theoretical gain achieved by the currently available transmit diversity technique. “Ruckus doesn’t have this limitation because we implement beamforming at the physical layer using smart antenna arrays on top of whatever 802.11 chipset is being used.”

Furthermore, beamforming using omni-directional antennas wastes RF energy, causes interference and provides less than optimal control over Wi-Fi transmissions because the antennas send and receive in all directions at all times. And since chip-based beamforming only works when transmitting, it does nothing to help APs reject interference when receiving data; forcing APs to lower the data rate when interference is experienced.

While chip-based beamforming provides some performance benefits to clients within an AP’s range, it does nothing to increase the Wi-Fi “cell size” or coverage area. Without being able to fully focus RF energy in any specific direction, the range of the AP will always be limited by the output power of the radio and signal gain of that antenna.

Many fail to realize that beamforming using only chip level signal processing actually works against 802.11n which is predicated on spatial multiplexing.  Spatial multiplexing calls for deploying antennas far apart to gain as much diversity as possible.  But with beamforming, antennas need to be close together to avoid poor performance and weak signals. Ruckus has solved this problem by adding an adaptive, software-controlled antenna array that is configurable to compliment any and all 802.11n transmit modes.

Patented BeamFlex combines antenna beamforming with standard 802.11 chips
In stark contrast to chip-based beamforming, Ruckus Wireless has developed a patented, pattern-agile antenna technology called BeamFlex. BeamFlex combines beamforming at the physical layer, using smart antennas, with sophisticated client feedback mechanisms without requiring any modification to clients. This ensures the highest performance levels while extending signal range and rejecting interference by allowing Wi-Fi signals to be directed, on a per packet basis, over the best possible signal path for any given client.

With BeamFlex, physical antenna elements are combined in real time to form thousands of antenna patterns. For every packet, antenna control software learns and selects the optimum combinations as clients roam. This allows for unprecedented reliability by providing complete control over Wi-Fi signals and focusing RF energy only where it’s needed while not creating additional interference.

BeamFlex was specifically designed to take advantage of multipath environments. By controlling the form and direction of the transmission and reception of multiple Wi-Fi signals, higher data rates are achieved because interference and packet loss are avoided. Wi-Fi systems not employing automatically-controlled directional antennas are forced to lower their data rate when interference and packet loss is experienced thereby negatively affecting performance for all clients using that system.

BeamFlex cost effectively adds value on top of standard 802.11n chips, unlike any other Wi-Fi technology available today that purports to use beamforming.

Ruckus BeamFlex (Smart Wi-Fi):
* Continuously calculates and tracks the best signal path for all clients based on explicit performance feedback from each client.
* Adds a software-controlled intelligent antenna array on top of any standard 802.11 chipset.
* Automatically optimizes for both beamforming and spatial multiplexing.
* Offers over 4,000 different antenna combinations that can be used to form and direct Wi-Fi signals on a per packet basis to any client for ultra-reliability and performance.
* Provides system-level signal gain of up to 10dB and interference rejection up to 17dB.
* Delivers a two-to-four fold extension of signal range.
* Was designed and optimized for multipath environments to create different patterns which reduces multipath fading and mitigates interference.
* Simultaneously uses advanced 802.11n features including spatial multiplexing, transmit diversity, beamforming and maximal ratio combining for greater reliability and performance.