Since the iPad was released, it has received a mixed welcome within Enterprise environments. While a lot companies have at least some plan to move forward with iPads, these drivers are usually coming from the business side, instead of IT. In-fact, most IT shops are being dragged into IOS support with strong reluctance.
The broad questions which are causing resistance can be summed up in one word: SUPPORT. IT departments must figure out how to support the device in multiple areas. Information integrity and control, end-user support, and connectivity support all must be dealt with. Since this is a networking blog, I want to deal with the last one; and will do so in the next two articles.
Supporting iPads on the network is more complex than connecting them to an SSID and providing login credentials. If we look at the standard iPad user in most organizations, we see a highly mobile user, users who also have laptops. Most of these users requested an iPad after having a positive experience with their company issued iPhones. That translates to a user having three wireless devices at there desk at any given time: their laptop, their iPhone and their iPad.
To understand the problem this creates, let’s look at how we survey for a wireless network. There are two considerations: coverage and capacity.
A survey can be based on square footage, and provide a certain RSSI from wall-to-wall. This is a perfectly acceptable way to survey if everyone has their own office. However in Cube-ville, a single AP may cover 100 desk or more. If each desk has one wireless device, you now have a physical medium (the channel or airspace) that is incapable of supporting all of the connected clients.
The other way to perform a wireless survey is based on capacity. In a high capacity environment, the wireless spectrum, not the AP is the bottleneck. More on this later…
In a capacity based scenario, a number of desk are chosen, lets say 25. For every 25 desk, there is an AP. Those AP’s are placed based on coverage area, and in to minimize channel overlap. For the same 100 desk in Cube-ville, you now have 4 AP’s. Since there will be channel overlap, the radios are turned way down, and in general, the physical medium is now capable of handling the number of clients.
Taking this environment to the next step, each desk gets an iPhone, and a few months later, 1 in 4 request an iPad. We can safely assume that complaints will begin coming into IT about the wireless network. The
AP airspace that was previously servicing 25 clients now contends with 62 per AP. Time for another wireless survey and at least twice as many AP’s!
Now we can see the problem that many companies are facing. The i-devices are here, and businesses seem to love them. The network team must begin planning and building now. I would like to make a few suggestions which might keep network teams from finding themselves behind the eight ball.
- Budget to begin surveying your high density environments now.
- Develop a plan for support, complete with timelines and cost. Present this to the highest management level you can reach, so that it can be considered as the business begins planning device deployments.
- If your company has a charge-back system for devices, be certain a cost is associated with each IOS device to support the wireless network going forward.
- Be certain to include a survey and additional equipment as a cost of any iPad rollout projects, make certain the business can see the total cost of deploying iPads and iPhones.
- Finally, be first in line to get an iPad if you don’t already have one. You can’t support what you don’t understand; besides, it really is a great device.
I realize that there are other options out there other than the “i” devices. However, I haven’t heard of, or seen, a single enterprise level roll out. However, these rules apply to the world of Android and Windows too. More devices per square foot equals more demand on the wireless network.
Increasing AP density may not be always needed or even a good solution.
I support Cisco devices in high density environments. I’m replacing 1242 to 3600 series that allows to put more clients on the same AP, using both 2,4Ghz and 5GHz bandwidth. In a public installation we have today at least 50% 802.11n clients and I expect to reach 75% soon. Using omni directional antennas instead of sectorial/directionals helps to keep the specrum clean.
There’re many best practices for high density environment and quite often the number of APs is not doubled, just increased a little bit:
Click to access cisco_wlan_design_guide.pdf
Thanks for your comment!
I agree with you that using 5ghz changes things dramatically. If we are comfortable with 35 clients on each band per AP, that means we can basically support 24 desk that have 3 devices each. However, in cubeville, that isn’t a lot of space at all.
Using both bands (3502’s) on a deployment that I just finished which services ~1000 users, we doubled the original AP density. The original density was based solely on dbm and square footage. We did have wall-to-wall coverage, it just wasn’t usable.
If we had not been using both bands, we would have needed more than 3 times the number of AP’s required for basic wall to wall service. Even with that density, we still see AP’s that have more than 45 clients on a single band occasionally.
As for antenna selection, Client Link makes the use of omni’s a lot more important. In most of our office environments, we are deploying the 3502i’s so antenna selection is a mute point.