To Surf or Not To Surf. That Is The Question. - Devin AkinBy CWNP On 08/26/2013 - 7 Comments
Guest Blog by Devin Akin of Aerohive Networks - In this post, Devin, with the help of several CWNE reviewers and contributors, discusses the various considerations to be made when implementing 802.11ac in enterprise networks.
The 802.11ac amendment to the 802.11-2012 standard is currently in Draft-5, and equipment (access points and client devices) based on 802.11ac started releasing into the market in late 2012. Enterprise-class equipment has now begun shipping from various vendors, and is being released into the market in “Waves.” Because the industry has chosen “Waves” as the way to describe how 802.11ac technology will enter the market, I’ve chosen the term “Surf” as a word analogous to “Buy.”
Wave-1 equipment will, in general, be characterized by the following capabilities:
- 5GHz only operation (applies to all “Waves”)
- Up to 80MHz channel width
- 256QAM modulation
- Up to 3 spatial streams (3SS)
- Single-User MIMO (SU-MIMO)
Wave-2 equipment will, in general, be characterized by the additional benefits:
- Up to 160MHz channel width
- Transmit Beamforming (TxBF)
- Up to 4 spatial streams (4SS)
- Multi-User MIMO (MU-MIMO)
Note: All references to 802.11ac (hereafter denoted as just 11ac) in this blog are strictly regarding Wave-1 802.11ac unless stated otherwise.
Disclaimer: I reached across the aisle to well-known and respected CWNEs to co-author the content of this blog so that any bias I might have would be neutralized. Yes, this blog is that important to us, and I hope, to you as well. (contributing CWNEs listed at the end)
Any of you who’ve known me very long know that I quickly anger in the presence of mis-marketing. So, with the help of some beloved CWNE friends, I’ve created two lists. The first list contains the benefits of 11ac and reasons that you could state as real and actual justification for buying an 11ac Wi-Fi system (or upgrading to one). The second list contains reasons why you should consider not upgrading to 11ac. Consider this a sort of Ben Franklin Balance Sheet to help with indecision.
Reasons To Surf
Technical and Support Benefits
Due to better silicon (radio hardware) and modulation (256QAM) with 11ac radios, we are able to achieve:
- Higher peak data rates (for capable clients)
- Improved airtime efficiency
- Better rate-over-range (same data rate at longer distance or higher data rate at the same distance)
- Aggregate cell capacity
11ac APs will be more powerful (e.g. CPU), so they will be capable of more functionality and more simultaneous functionality than equivalent 11n APs. As examples, this can mean improved
- High-density handling
- Higher throughput capability
- Better application-layer flow identification
Manufacturers will support/warranty 11ac capable hardware for longer than 11n hardware because 11n hardware will be End-of-Sale (EoS) and End-of-Life (EoL) prior to its 11ac counterpart. This also applies to the software support for these hardware products.
Need More Capacity
If your 11n network is optimized for airtime and throughput and you still lack enough capacity, you may be ready to upgrade in the physical areas where your 11n network has reached its limits. Before such an upgrade, assure that you’ve followed your manufacturer’s high-density design guide, focusing on items such as removing legacy 11a/b/g devices and proper RF design for coverage and capacity. Also verify that most of your client devices are currently 11n and that you are moving to 11ac clients as rapidly as possible. It might also be a good idea to assure that you’ve measured and understand average/peak loads and utilization variability across your AP deployment over relative time periods, verifying that you understand specifically where (and what type of) improvements are needed before the upgrade.
Maximizing Client-Side Investment
For organizations with an early adoption strategy for 11ac client-side devices, an 11ac infrastructure investment maximizes the usefulness of the client-side investment. It’s true that using 11ac clients, even with an 11n infrastructure, still offers benefits (e.g. rate-over-range and less retransmissions due to better receive sensitivity), but the benefits are increased when both sides of the connection support 11ac.
Additional benefits can include enhancements proprietary to the client and AP chipsets. For example, Broadcom’s TurboQAM technology, if implemented on both sides of the client/AP connection, can enhance throughput in 2.4GHz. This enhancement will most often be found in new 11ac-enabled APs and clients.
One final consideration is Transmit Beamforming (TxBF). The Wi-Fi Alliance is planning to certify TxBF in Wave-2, but some Wave-1 devices (depending on chipset capabilities and driver development) support TxBF. The benefits of TxBF are up in the air at the moment because they depend on several variables (environment, client/AP support and interoperability, extent of client mobility, and more). Testing will prove its value at some point in the future.
You’re Ready For Lifecycle Upgrades Now, Not Later
If you have an 11a/g infrastructure you need to upgrade to something due to a project or other drive that requires a Wi-Fi upgrade immediately (rather than waiting 1-2 years for Wave-2). If 11ac is being offered at the same price as 11n, it certainly makes sense to upgrade directly to 11ac rather than to 11n. If there’s a price differential between 11n and 11ac, evaluate according to your client/application needs over the expected lifetime of the AP. It’s important to note that Wave-1 equipment is an incremental technical improvement over 11n, working much in the same way, so risk of instability is somewhat low. In contrast, Wave-2 introduces new technologies (e.g. TxBF, MU-MIMO), which are not mature and introduces risk of instability.
If your access-layer wired infrastructure has been upgraded…
- Switches with 1Gig downlink and 10Gig uplink
- 802.3at (PoE+) capability with enough power budget and ports to power the desired number of APs
- Data cabling is at Cat5e or better
…then you might be ready to look into 11ac. Upgrading APs for a faster physical layer (PHY) won’t help if your wired infrastructure is a bottleneck. 11ac APs are capable of very high peak data rates (up to 1.3Gbps), which can translate into ~50%+ of the data rate in actual throughput for a single client without contention/interference. When added to the 2.4GHz 11n radio’s throughput, it can add up to 700-900Mbps of throughput for high-end APs, so 1Gig Ethernet downlink is a reasonable requirement. Note that if you are using 802.3af (standard PoE), then you should understand the limitations of any 11ac AP you may purchase that would operate on standard PoE. Not all 11ac APs have the same power consumption requirements.
If you are an early adopter of technology, have extra money to spend on 11ac, and don’t mind the expected headaches that come along with any new technology, then upgrading to 11ac may be OK. Some organizations want to “lead the way” as early technology adopters, and if that’s your situation, just be prepared for the expected challenges.
Reasons NOT To Surf
You (nor I, nor we) know enough about designing for, deploying, or troubleshooting 11ac technology yet. There’s currently very little instructional information on 11ac, and there are very few actual deployments of 11ac in the market today. As the technology is deployed into various vertical markets and into various scenarios, manufacturers will learn the caveats to pass along to their partner and customer bases. Technology book authors and consultants will learn through experience what works and what doesn’t. It simply takes time to learn all of the “gotchas” of any new technology. For example, what about channel planning? With the addition of 256QAM modulation and its practically-extreme power requirements, you can imagine the CCI and ACI issues sure to arise if the network is designed improperly?
-59dBm or better at 20MHz (-57dBm for top data rate)
-56dBm or better at 40MHz (-54dBm for top data rate)
-53dBm or better at 80MHz (-51dBm for top data rate)
-50dBm or better at 160MHz (-48dBm for top data rate)
What about the issues that could arise out of dynamic bandwidth expansion with RTS/CTS? Will it work properly? Should we enable it? What about the situation that could arise when adjacent non-overlapping 40MHz-channel APs expand to use the same 80MHz channel? Perhaps it could be OK at low-density, but more problematic at high-density. See what I mean? You, nor I, nor we, know enough yet. Watch, listen, read, touch, and learn. We’ll all figure this out together.
CWNP is a great vendor-neutral place to start learning the technical details of the 802.11ac amendment and the 802.11-2012 standard. Manufacturers are releasing 11ac whitepapers and other educational documents regularly, and there are finally some 11ac books hitting the market. Education is your best offense and defense. Reading is where you start.
Use What You Have First
Your 11n network probably isn’t working just the way you want it to yet. Am I right?
- Is it properly designed, installed, configured, and optimized?
- Are you still doing regular troubleshooting?
- Is it optimized for your installed client base?
- If an experienced consultant gave your 11n network a thorough review, would you expect him/her to find any significant issues?
If your 11n network isn’t yet optimized, then you’re probably not ready to tackle adding 11ac into the mix with all of its technical differences.
11ac is new, and you haven’t adequately tested it yet. Have you tested your clients with 11ac APs for compatibility and to make sure your device drivers work properly? Client-side driver issues can be one of the most time-consuming and difficult problems with Wi-Fi in general. Like Keith Parsons says: Test, Test, Test.
You haven’t adequately vetted enough 11ac systems yet to know which is the best fit for you. As of this writing, there are very few available 11ac APs, and there are no independent test results available. Test results will vary widely due to early client device variability.
If you expect to continue having more 11n client devices than 11ac client devices for a significant period of time, then you may just want to stick with your 11n infrastructure. There are some benefits (rate-over-range and receive sensitivity at the AP) to upgrading to an 11ac infrastructure while using all 11n clients, but it’s not significant enough to warrant spending the money on an upgrade.
Use of 80MHz channels are unproven in enterprise environments, where significant channel re-use is typically required. If 80MHz channels turn out to be a bad idea, this could negate one of the major marketing reasons for upgrading to 11ac. 80MHz channels may be OK for single-AP (and sometimes two-AP) branch offices and homes. If the gains that you get from…
- 256QAM modulation (typically good for up to ~12 meters or ~40 feet, depending on several variables)
- Airtime efficiency
- Rate-over-range due to receive sensitivity
- 40MHz channels (same as with 11n)
…is sufficient to warrant purchasing 11ac in your situation, then OK, but I wouldn’t consider 80MHz channels a valuable portion of the equation until you’ve done some testing with the specific type of gear you plan to deploy.
You don’t have any professional tools to design or troubleshoot 11ac properly yet. If your infrastructure manufacturer includes some troubleshooting tools within the controller, management system, or AP, evaluate how useful each of these tools are before proceeding with a purchase. A good example of a tool that you need in most troubleshooting situations is a protocol analyzer (“a sniffer”). Sniffers depend on having a radio that supports the new PHY (in this case, 11ac). Until 11ac-enabled troubleshooting tools become available, it will be difficult to troubleshoot and optimize your wireless environment.
If you have a large number of APs, it’s worth noting that premium-grade (high-end) 11ac APs will use more power than their 11n counterparts. This may not seem like a big deal, but if the differential is 3 watts, and you have 10,000 APs, that’s 30,000 watts of additional power. I don’t know about you, but I wouldn’t want to pay that power bill each month. J
On the flip side of a previously-mentioned item, if you haven’t upgraded your wired infrastructure (10Gig uplinks, 1Gig downlinks, PoE+ where required, and ubiquitous Cat5e cabling), then you may not be ready to invest in 11ac because there’s a potential backhaul bottleneck. If your infrastructure falls short of these requirements, take a good look at your expected throughput.
To dig into one of these areas more closely, if the proper amount of Power-over-Ethernet (PoE) is not provided to an access point, it may not be able to fully enable all features (Gigabit Ethernet ports, Wi-Fi radio chains, etc.). The disabling of radio chains will result in fewer spatial streams, lower data rates for high-end clients, less airtime efficiency within a channel, and lower overall capacity per channel.
Wave-1 vs. Wave-2
Wave-2 11ac will offer Multi-user MIMO (MU-MIMO) around Late-2014, giving a switch-like experience on the downlink to up to 4 clients simultaneously. The additional benefits over Wave-1 are listed above. Consider whether you need/prefer Wave-1, Wave-2, or a mix of the two over time (which is often the case) and whether waiting is beneficial to your organization. It’s important to emphasize that the time gap between Waves should be a significant deciding factor on when to buy 802.11ac infrastructure. Wave-2 is an unknown at this point, and reasonably it could be 12-24 months before the market sees any proven/tested/certified enterprise-class Wave-2 equipment. If that uncertainty and timeframe isn’t to your liking, consider opting for Wave-1 sooner rather than Wave-2 later.
Wi-Fi Alliance Certified
Make sure that any client-side or infrastructure-side 11ac equipment is Wi-Fi Alliance certified. If not, don’t buy it. You’ll have enough headaches without trying to reinvent the interoperability wheel.
That was a lot, yes. There’s much to understand about the technology and about why/why-not to buy it. Buying 11ac equipment is specific to your situation, and we wanted to give you the tools to make a good decision based on what we know so far (which isn’t comprehensive). We’re certainly open to suggestions, feedback, and input based on your knowledge-of and experience-with 11ac technology. This blog is meant to be educational, and hopefully your comments will follow suit.
CWNE Reviewer Credits:
Devin Akin, CWNE #1, Manufacturer
Kimberly Graves, CWNE #2, Manufacturer
Keith Parsons, CWNE #3, Consultancy, Reseller, & Training
David Coleman, CWNE #4, Manufacturer
Marcus Burton, CWNE #78, Manufacturer
Andrew von Nagy, CWNE #84, Manufacturer
Tom Carpenter, CWNE #104, The CWNP Program Tagged with: WiFi, 802.11ac, Devin Akin, upgrade, implement, maintain