It's a fairly common scenario: You're working to update existing infrastructure to an 802.11ac wireless LAN, and...
the inevitable question of access point locations arises. Is it OK to simply swap out the old APs and put the new ones in the same locations? It's a reasonable inquiry, and it's also one that can be fairly polarizing depending on your frame of reference and job title.
As with many things wireless, there is no simple answer that applies to all 802.11ac wireless LAN projects. Let's consider under what circumstances reusing the existing cable plant is acceptable and when it's not.
Opinions, perspectives and reality
If you're in the business of designing networks for a living, you might insist that every tech refresh demands a new plan, period, for best performance. If you're on the facilities side, you might be thinking, "Uh, that cabling is supposed to be good for 10 to 15 years, which is like two or three AP upgrade cycles." And if you're paying the bills, you want to maximize any current investments in cabling and switches and get the longest service you can out of them.
Nobody's wrong here, and everyone's opinion has merit. But reality will vary from situation to situation.
What are you building on, and why?
Wi-Fi upgrades are driven by any number of factors. If you're on an old 802.11g design that's working for a low client count, but are dealing with end-of-support APs, you will do just fine with new .11ac access points on existing cabling -- assuming you are accounting for new Power-over-Ethernet needs -- as long as your client numbers, types and needs won't drastically change. Just keep in mind that many older coverage-oriented designs -- fewer APs, stronger radio power -- fall down when beefy laptops are superseded by mobile devices with lesser radios in them.
If the same legacy design is being stressed by significantly larger client counts, types and requirements, you have some changes to make when considering an 802.11ac wireless LAN upgrade. Whether you scrap the entire current layout or just augment it will depend on your budget and environmental constraints.
As long as you have properly installed unshielded twisted pair that legitimately passes gigabit certification, you probably have the option to make use of at least some existing cable. Make sure you work with a WLAN designer who has an open mind and who listens to what you want, rather than one who goes straight to, "This is what you need." Wi-Fi is flexible, and your design partner should be, too.
What if you have a robust dual-band 802.11n network that was professionally designed and are upgrading just because it's lifecycle time? If it's all working well now in both bands -- and you don't expect significant changes to your overall or per-AP client counts and types -- then, by all means, go for it. But also make sure you verify things are good afterward.
Don't bungle the antenna thing
If you do decide you can rip and replace and use existing cabling, make sure you don't botch it all by changing the antennas in use. If you are using external or internal omnis, stick with that on the replacements. And if you are using external directional antennas, know that most new APs won't be compatible with many older antennas, based on the number of radios and whether each output stub is single-band or dual.
If in doubt, get professional help. And don't be afraid to buy antennas from the likes of Ventev and AccelTek -- versus Cisco or Aruba -- to potentially save a lot of money.
Final word: Maybe you can
This is a short narrative on a big question that doesn't have a single answer. I am on all sides of the issue, as I design and run networks and also need to watch budget dollars closely as a purse-holder. Whether you can reuse existing cabling and AP locations for .11ac updates is not a yes-or-no question, but knowing what goes into arriving at the right answer will help you get there.
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