The Ruckus Room

Cisco Validates Smarter Wi-Fi, Sort Of.

Informants have hinted that Cisco is planning to unveil a new line of 802.11n dual band access points next week.

What's more Cisco says these APs will use the "built-in" 802.11n beamforming functionality for the first time. 

Beamforming is an option in the 802.11n standard and has been integrated into the 802.11n chipsets provided by Atheros and Broadcom.

No surprise to most, Cisco seems to be following the path of least resistance by relying on chip suppliers for each and every morsel of RF technology advancement.

That said, Cisco's validation of beamforming is a big acknowledgment to the industry that more needs to be done to make Wi-Fi more reliable at the physical layer. Ruckus was conceived around this concept - making WI-Fi more reliable.

The problem is, the "beamforming" called out by the 802.11n standard does very little to solve this problem.  In other words, not all beamforming was created equal.

Beamforming can essentially be performed in two ways:

1. Mathematical beamforming
   This is achieved through digital signal processing in lower levels of the chipset (baseband and multiple radios). This gets all the academic attention and what most people mean when they mention beamforming.
    
2. Physical beamforming
   This is achieved through the use of adaptive directional antennas and best path selection algorithms that dictate that actual form and direction of radio signals through the RF domain using thousands of antennas and actual client feedback (click on figure below) to optimize things.

Mathematical beamforming at the chip level tells the system which antennas to use for a given client and has theoretical maximum limits (eg. 3dB of gain for two radio chains). But nearly every 802.11n access point on the planet uses omni-directional (rubber duck) antennas that constantly blast out and receive signals in all direction providing next to no way to combat environmental problems.

This type of beamforming can't optimize the actual form and direction of Wi-Fi signals and has no real-time adaptive capabilities. Therefore it can't determine the actual performance of a given path, change it if there's a problem or reject or avoid interference as it is experienced.

Testing has shown that the slightest change in the way 802.11n antennas are pointed or the AP is positioned results in wildly different performance levels.  We've seen fluctionation from 5 Mbps to 80 Mbps in performance by simply moving the AP 90 degrees or the client to a different locations.

Physical beamforming goes waaaaaay further. Physical beamforming adds a whole "subsystem"  on top of the standard chipset that allows complete control over Wi-Fi signals. The basic idea is to improve performance by creating several independent signal paths between the transmitter and the receiver.

What's important here is that physical beamforming is adaptive - constantly adjusting Wi-Fi performance based on real things happening in real time.  Here's how it works (for the most part):

A miniaturized antenna array provides thousands of antenna combinations that smart software algorithms use to form very concise and optimized signals. These same software algorithms use actual feedback from each client to select the best performing signal path at any given time.  We use the analogy of holding a flashlight in your hand in a dark room vs. turning a flood light on overhead.

This translates into three very important benefits for users:

1. better (read more consistent) performance over longer distances
2. more reliable connectivity (interference rejection helps avoid Wi-Fi "flakiness")
3. Non disruptive (no client support required to achieve these benefits)

While mathematical beamforming requires chip-level cooperation from both sides and hence requires standardization, physical beamforming gets that cooperation for FREE from the 802.11a/b/g/n protocol. And with physical beamforming there are effectively no theoretical maximum gains limitations. With our "smart antenna" system we've seen system gains of 9dB and interference rejection of 17dBi.

So now you know.

Femtomorrow? Wi-Fi Regardless.

Have femotocells become the next WiMax (read: lots of pilots, few commercial deployments)?

Like WiMax, there's so much written about this new technology but very little real-world services (so far). I've yet to see any device with WiMax support. But then again, I don't get out too much.

Femtocells are fully featured but very low power mobile phone base stations, connected using standard broadband DSL or cable service into the mobile operator's network (click on diagram). They offer excellent mobile phone coverage at home for both voice and data, but at lower cost than outdoor service.

Nearly every carrier with whom we've spoken (and we know them all) has an interest in or is planning some sort of Femto trial. From a handset perspective, Femtocells provide a clear advantage in that they function just like another cell tower so they can potentially leverage standard mobile roaming (click on diagram).

The femtocells themselves look very much like Wi-Fi broadband modems, and some vendors are planning to incorporate all three features into a single box (Wi-Fi, DSL and Mobile). But many consider Femtocells to be "irrelevant" in many countries.

Unlike Wi-Fi, these devices use licensed radio spectrum, so must be operated and controlled by a mobile phone company. Thus it will work with only one mobile phone operator, and thus encourages all users in a household to switch to the same network operator. But skepticism remains.

This skepticism is accompanied by quite a few challenges:

• Interference - The placement of a femtocell has a critical effect on the performance of the wider network - and this is one of the key issues to be addressed for successful deployment.
• Spectrum planning – Each Femtocell unit will affect the overall spectrum planning of the operator which brings up not only planning but also deployment challenges (e.g. what happens if the Femtocell unit is moved?)
• Timing - When will Femtocell really be ready for mass deployment?
• Device support - (specifically laptops) – Many vendors and operators assume a Wi-Fi interface on their Femtocell device to handle laptops. Not so.
• Scale (management) – Operators will need to scale their backend systems to handle not 1000s of towers but potentially millions... that’s a very different problem to solve.
• Cost
• Business model concerns

But the bigger question burning in the minds of many providers:

What's the relationship between Wi-Fi and other broadband technologies
like Femto, WiMax, and 3G/LTE?

It's our not-so-profound belief that (as you'd expect):

Wi-Fi is the ultimate complement for all these broadband wireless technologies.

Why?

• Wi-Fi is everywhere
• Wi-Fi is supported on nearly everything now
• Wi-Fi is arguably the most economical technology for the last 100 meters
• Wi-Fi helps reduce spectrum planning issues
• Wi-Fi augments coverage holes
• Wi-Fi minimizes huge investments in broadband wireless equipment
• Wi-Fi is ideal for offloading data from overburdened 3G, LTE, WiMax networks