If you have occasion to step foot on a university campus this fall, once thing is certain: you will see more wireless devices than ever before. Students and faculty across the globe will be flaunting their iPhones, iPads, BlackBerries, Android (News - Alert) devices, and the latest notebooks and netbooks, allowing them to communicate and study anywhere on campus. It’s just one example of the surging growth of WiFi (News - Alert) usage in the enterprise space today, which, in many cases is replacing traditional wired networks.
Take Carnegie Mellon University, for instance, which, like most schools, has typically offered students the option of wired or wireless access in their dorm rooms, until this year, when it eliminated the wired offering for all but a few special cases. Instead, the university deployed Xirrus WiFi arrays throughout its campus, telling students they would have to file a special request form in order to have their Ethernet ports activated. As of a few weeks ago, only a dozen or so students had filed for wired connectivity in their rooms.
“These students are going to be coming out of this school and virtually every other university in the world over the next four to five years and will show up in the workforce not knowing what an RJ-45 is or what it looks like,” says Xirrus CEO and founder Dirk Gates (News - Alert). “They are also going to expect wireless in the enterprise.”
But, as the graduating class of 2014 heads off for its freshman year, already today, many enterprise workers expect to have WiFi access at work. Largely, the demand is being fueled by the proliferation of wireless routers and WiFi-enabled devices in the home, including not only those same devices used by students, but also TVs, DVD players, game consoles, radios, and soon, many home appliances and other devices that will be wirelessly connected to smart homes.
“These factors, as much as anything else, are going to continue to drive forth that revolution from being all-wired enterprises to being all-wireless,” says Gates.
Behind this dramatic growth of WiFi adoption is the evolution of the 802.11n standard, which is supported by virtually every new device and allows wireless technology to match wired from both a speed and performance perspective. It portends only a short period before the balance of power in the network world shifts from wired to wireless. In addition to the convenience and flexibility of wireless, the cost effectiveness of deploying a wireless network over Ethernet makes the decision an easy one.
“It’s a question of time to value,” says Gates. “Not only is it far more cost effective, but the time it takes to make you facility ‘wirelessed’ is much shorter than the time to wire it.”
According to Xirrus, when considering a generous cost for cable drops, the cost of switch ports, and other associated costs, the cost per user to install Ethernet to each desk and each user starts at around $400 per user. Deploying a very dense, rich wireless solution, even at less than five users per radio, can be done for less than $100 per user.
Even in buildings with existing Ethernet cabling, the trend is also apparent, though the transformation is not quite as radical. Whereas enterprises once expected to replace their Ethernet switches every three to five years, many are now extending that to seven or ten years, riding that investment as long as it is useful, while building out a wireless infrastructure that will form the basis of its future connectivity.
You Can’t Have Too Many Radios
The concern over enterprise-wide WiFi has always been its ability to handle mission-critical applications but, with the 802.11n standard in place, the technology is capable of handling most enterprise applications today. Not all WiFi networks are equally capable, however, due to a lack of proper education among IT departments (and often the executives who have to cut the checks for the investments in wireless technology). According to Gates, the most common mistake in enterprise WiFi deployments – which becomes apparent quickly as employees come to work and data rates drop – is underprovisioning.
“The industry is still learning, as a whole, how to properly and adequately deploy wireless networks to replace the wire,” says Gates. “It’s not as simple as taking what you do at home with a single AP covering the house and trying to translate that into the enterprise.”
Home and older enterprise-class APs are designed for maximum coverage areas and thin density, primarily because few users are on the WiFi network. With the proliferation of WiFi-enabled devices, enterprises must shift their thinking from a coverage model to a more robust density model, which basically means they need to deploy more wireless radios than in the past.
Most enterprise Ethernet networks are overdeployed by a factor of two, because the logical choice has always been to pull two cables instead of one to allow for growth. In fact, if you look at today’s businesses, it’s likely you will find twice as many Ethernet switch ports deployed as there are users.
The opposite is true for WiFi networks, where the prevailing strategy has been to deploy the minimum number of APs that will still allow enterprise-wide coverage. The limited deployment of APs has resulted in double-digit users per AP.
“The dichotomy between wired and wireless has to shift; it almost needs to be flip-flopped,” suggests Gates. “Businesses need to put up as many wireless radios in their wireless infrastructures to drive the number of user per radio down to something close to one, while right-sizing their Ethernet networks so they don’t have twice as many switch ports as they need.”
It may seem counterintuitive to deploy WiFi at densities that will allow low single-digit users per AP, but the logic is sound. We have all experienced slow data speeds on congested WiFi networks, and maximum density relieves that added burden on the networks and allows each user to function at maximum efficiency.
That model was the founding vision behind Xirrus and its WiFi arrays: How can I get more WiFi radios in my wireless infrastructure in a cost-effective manner? It’s not an original solution. Rather, it is one that drove the explosive growth of the cellular market a decade ago. Wireless operators faced a similar dilemma, needing to expand their infrastructure tenfold to provide service to a rapidly increasing user base.
All you have to do is drive around town to see their solution. Instead of deploying single-radio base stations, they put an array of radios on their towers, each with a directional antenna facing in a different direction covering a different area. This way, they were able to maximize coverage while limiting the number of towers, which also meant having to backhaul fewer base stations into their core networks.
Gates took that same model and applied it to WiFi, placing multiple radios in the Xirrus arrays and using directional antennas, with a net result of providing a richer, denser WiFi infrastructure with more radios but fewer devices. In the typical enterprise, this can result in as much as a 75-80 percent reduction in APs, not to mention their associated cabling and switch ports.
“Instead of trying to figure out how to position an AP and try to cover 50 users with it, I would position a set of APs and try to cover certainly no more than 10, but maybe even less than five users per radio,” he says.
These Bands Aren’t Silly
Following just behind radio to user density in terms of what IT departments need to understand is how to effectively use WiFi spectrum.
Most home APs contain one or two radios – one operating at 2.4 GHz and often a second operating at 5 GHz. This is adequate for most homes, where the 2.4 GHz band has long been seen as the superior alternative due to its longer range. The challenge with taking that model to the enterprise environment is that it only has three non-overlapping channels, whereas the 5 GHz band has 24, and its range can be easily increased through the use of directional antennas.
Because the 5 GHz band has eight times as much spectrum as 2.4 GHz, a critical part of successful enterprise WiFi deployments includes installing eight times as many 5 GHz radios as 2.4 GHz radios, along with ensuring there are eight times as many users operating at 5 GHz to make use of the additional spectrum.
Today, most laptops are capable of operating at 5 GHz – as is the iPad, which is being more commonly deployed as an enterprise tool. Still the most common enterprise handhelds, BlackBerry devices are also dual-mode capable, as are most WiFi VoIP phones, such as those from Polycom (News - Alert) and Cisco. iPhones and Android devices still operate at 2.4 GHz, but it’s likely they, too, will move into the 5 GHz band over time, simply because of the operational efficiencies.
“In the home, a three-lane highway is fine and you really have very little interference because you don’t have a lot of people trying to get on the highway,” explains Gates. “But, in the office, if you have your choice between a three-lane highway and a 24-lane highway, you certainly want to get as many users on that 24-lane highway as you can, up at the 5 GHz spectrum.”
Range is Not Your Friend
The misconception that most deployments suffer from is that maximum range is important, which is why many IT managers seek to deploy consumer APs in their enterprises. Gates counters by claiming that, in the enterprise, “range is your enemy.”
For one thing, as range increases, so does interference due to larger coverage areas with more users. More importantly, though, with WiFi, data rates are inversely proportional to range, meaning that, the further a device is from its AP, the more dramatic the reduction in throughput.
For instance, if you are within 30-45 feet of your AP, you might be communicating with your network at 300 Mbps today – and in 12 months, that will likely increase to 450 Mbps. But, if you are 300 feet away or more, your data transfer rate might dip to 6 Mbps or worse, down to 1 Mbps at 2.4 GHz.
In an enterprise environment, where WiFi is a shared medium – at least until you’ve deployed at one or two users per radio – if your device is close to the AP and your data rate is 300 Mbps, you’re not impacting network performance much. But, as you move away from the radio and your data rate drops, you are taking exponentially more airtime to transfer the same data, which limits other users and brings the total throughput of the network down. A properly designed enterprise WiFi network has small cell sizes, where you have a small number of users who connect to each AP at very close ranges.
“You don’t want users connected at great ranges in the enterprise because it just destroys throughput for everyone else,” says Gates. “What you really want is a network where everybody can be connected at the maximum data rate.”
The overestimation of the importance of range only underscores the challenge with deploying inexpensive consumer APs in the enterprise. It results in a 1:1 ratio of 5 GHz to 2.4 GHz radios and an overdeployment of 2.4 GHz radios, but a severe underdeployment of 5 GHz radios. In order to take advantage of the 5 GHz spectrum, businesses have to deploy their networks such that the majority of users are operating at 5 GHz. Otherwise, says Gates, they are not deploying the best WiFi networks they can.
The Site Survey
Once enterprises understand deployment density, the differences between 5 GHz and 2.4 GHz, and range issues, they are ready to determine how to deploy their wireless networks, beginning with an active site survey.
While the industry as a whole would like to do away with active site surveys, they are almost as critical to a good network understanding the technology itself. Because floor plans don’t always indicate unexpected obstructions to RF signals, the only way to effectively determine the best layout for WiFi radios is to set an array on a tripod, as Xirrus does, and take live measurements.
While active site surveys can be less critical when overdeploying and underprovisioning radios, an intuitive approach, while often reasonable, cannot account for unexpected barriers, such as a stack of metal drawers.
Without an active site survey, it can be impossible to determine how many radios are needed, where they should be deployed to provide maximum efficiency and throughput. An active site survey allows for signal strength at every point in a building that guarantees maximum data rate, which is why it’s the first thing Gates recommends enterprises do when beginning to plan their WiFi deployments.
“You do an active site survey so you know exactly what you’re going to get when you actually tack up the network and put the final devices in place,” says Gates.
Of course, his company has a distinct advantage with its arrays, which provide greater coverage in each device, meaning they can conduct a site survey in a fraction of the time it might take with traditional legacy APs and controllers.
The Next Stage
From his days at Xircom to Xirrus, Gates has already witnessed a remarkable evolution in the wireless market, a growth that is set to accelerate over the next decade. Most market estimates show the overall Ethernet switch market at about $20B and declining or, at best, fl at. On the other hand, the WiFi market is growing at 25-30 percent annually.
Though it’s currently only a tenth of the Ethernet market, a 25 percent annual growth rate against a fl at market make it easy to imagine a WiFi market that, in five years, will be bigger than the Ethernet market in the enterprise.
The fundamental changes during that period, according to Gates, will be in performance. Already, with 300 Mbps date rate, WiFi is beating the 100 Mbps Ethernet that is in most businesses today. The 802.11n standard already provides for speed increased up to 600 Mbps, which Gates thinks will come in about three years.
There are also standards bodies in place already looking at Gigabit speeds for WiFi, some of which will be accomplished in the 5 MHz band by expanding channel size and using creative modulation schemes, but other groups are also looking at multi-Gigabit communications in the 60 GHz range.
The speed and performance increases are also likely to create a demand for wireless backbones in the enterprise, where access devices use on set of radios to create a Gigabit-speed wireless backbone, and the remainder of the radios will continue to provide edge connectivity.
Gates says Xirrus has some customers already daisy chaining its arrays in this way, bonding three radios to deliver WiFi to areas that are too difficult to reach with a wired backbone, such as a smaller building across the street or in manufacturing facilities where it’s simply too costly to run cable to the factory floor. He thinks the practice will take off in the next 5-10 years as WiFi eclipses the Gbps mark.
Though we’re still at least fi ve years away from that, the performance improvements the WiFi market is set to experience will finally lay to rest any lingering questions regarding its performance against wired networks.
“Every 12-18 months, you will see the speed increase another 150 Mbps,” says Gates. “I’m fairly confi dent the next crop of kids going back to school are going to be carrying 450Mbps capable WiFi adapters in their notebooks and, probably two years from that, you’ll be at 600 Mbps.”