May 272011
Xirrus, Dense Wireless Solved

It wasn’t too many years ago that you could calculate the number of wireless clients you’d have to support simply by counting heads. Oh I have 100 people to support here? Okay, roughly 100 wireless clients then, max. Well that nice, simple equation is about as true as 1 + 1 = 1 nowadays. Think of all the things you might possess that have a Wi-Fi chip in them. In my workplace alone we have:

  • just about every cellphone (and I know a lot of people who regularly carry 2 phones with them for work vs personal)
  • laptops
  • tablets (iPad, Xoom, etc.)
  • Desk phones (Cisco 9971)
  • more than I’d like to admit, weird, random things discovered while scanning

My most accurate calculation is figuring a 4:1 ratio of wireless devices per employee. Think of your small 20 employee company. One normal access point could easily reach an area that 20 people would sit within. Yet if there were 80 wireless clients on that access point it could quickly get saturated. With cube farm layouts you could easily have hundreds of wireless clients within range of one access point. Typically in an enterprise world if you were to run into that situation you would have to deploy more access points in that area, not for range, but simply for throughput and load. Seems like more of a bandage on the issue than a true solution. Especially realizing the complexity of having multiple access points close to each other fighting in the same airspace. Well if you find yourself either needing more range out of single access point or more importantly needing to support a dense population of wireless clients then you should definitely look at what Xirrus has to offer.

Xirrus puts anywhere from 4 to 16 radios into an “access point” and in doing so truly solve your density issue with wireless clients. My example above is a manageable situation. Think about conferences or trade shows though and you see where there can be a huge demand for an access point that can handle hundreds of wireless clients within its range. I don’t want to go over all the technical specifications but let me point out a few of the most notable differences in this array. Instead of omni-directional antennas they use directional antennas covering the 4 basic directions (north, south, east, west). These 4, regardless of your model will be the only dual-band a/b/g/n radios. So their basic model, the XN4 has these 4 radios, the XN8 has these four and then adds 5ghz a/n radios in the NW,NE,SW,SE positions. There are XN12 and XN16 models each adding to your 5GHz band. As you can imagine, placing directional antennas in a circular array will give you a bit more range than an omni-directional one. As you move to the XN8+ they can more tightly focus the beam of the directional antenna giving an even greater range.

In the enterprise access point space there is a great need for wireless monitoring. In other words detecting other wireless signals within your air space so you can either move to a cleaner channel or identify rogue AP’s that should be shutdown or removed. Cisco has what they call Cisco CleanAir Technology. Its actually a great technology and Cisco implements it quite well. However one of your radio’s in a Cisco AP has to quickly switch to monitoring mode then switch back to accepting clients in order to maintain this discovery of your wireless signals. You could also buy an access point dedicated to monitoring but in a large deployment it would only monitor within the limits of its range. If you were to use a Xirrus XN8 you could designate one of the radios solely to monitoring this spectrum thus not messing around with that switchover to take clients, still having 7 left for throughput and you could do this for each access point increasing your monitoring coverage. From my initial research you could replace standard access points with ones from Xirrus at a 4:1 ratio quite easily.

The other nice tidbit these add are dual gigabit lan ports for either primary/failover or load balancing into enterprise switches. Considering the number of users they support this is almost a requirement but nice enough even for failover if you need to power cycle a core switch on your network these could stay up serving clients. These Xirrus Wi-Fi arrays lack virtually no core feature I could find within the enterprise AP space handily matching Cisco bullet point for bullet point. There are some differences of course in implementation but if you need to cover a further range, and more importantly a DENSE population of wireless clients you’ll want to check out Xirrus for a solution.