Tuesday, 5 May 2020

Cisco’s AI/ML can make your Wi-Fi 6 upgrade a success

Cisco Wireless, Cisco DNA Center, IOT, Wi-Fi, Networking, Cisco Tutorial and Material, Cisco Exam Prep

Upgrading to Wi-Fi 6 is not just about replacing your oldest access points. The true value proposition is in locating areas where specific Wi-Fi 6 features will improve the network performance and user experience. The AI/ML capabilities in Cisco DNA Center can help you find these upgrade opportunities.

Wi-Fi 6 has some new features that are useful in resolving what used to be unsurmountable problem areas in a wireless network. The first step is to understand these new Wi-Fi 6 features and the wireless challenges that they resolve.

As you are sitting at home reading this, you could be analyzing your campus wireless network for areas where Wi-Fi 6 can add the most bang for your buck. Wi-Fi 6 has some new features that are useful in resolving what used to be unsurmountable problem areas in a wireless network. Your Cisco DNA Center Assurance dashboard has AI/ML features that can allow you to find these areas!

The first step is to understand these new Wi-Fi 6 features and the wireless challenges that they resolve:

Poor performance in highly congested areas: OFDMA in Wi-Fi 6, allows multiple clients to transmit simultaneously in order to increase capacity in highly congested areas.

Poor uplink performance on mobile devices: Uplink sub-channelization in Wi-Fi 6 provides mobile devices greater radio transmit power without consuming more battery power. This provides mobile devices better Wi-Fi performance in challenging conditions.

High radio interference: The Wi-Fi 6 OFDMA uplink map creates a synchronization that leads to less interference in between clients and in between access points. Additionally, OFDMA allows clients to transmit on small channels at greater power making them much less susceptible to interference from other wireless devices.

The IoT small packet problem: IT teams with large concentration of IoT devices (manufacturing, process control, video surveillance, etc.) are very familiar with the packet processing bottleneck that access points can become. Modern Wi-Fi 6 chipsets solve this with powerful quad-core 2.2GHz processors that can process three times more packets than most 802.11ac access points and twelve times as much as most 802.11n access points. This processing power, combined with a well-designed access point data-forwarding mechanism, has the potential to eliminate most of the issues you used to have supporting IoT devices.

Now let’s look at how you can use the AI/ML in Cisco DNA Center to quickly locate areas in your campus network that fit these challenging conditions.

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Congested areas


Any simple network management system with wireless heat maps can show you areas of high congestion. But even older 802.11ac/Wi-Fi 5 (with multi-user MIMO) can handle most congested areas quite well. To get the best bang for our Wi-Fi buck, we only want to upgrade those areas where this congestion is affecting the performance and user experience. The Assurance section in Cisco DNA Center has an area called “Trends and Insights” where you can use AI/ML to compare just about anything on your campus network. You can compare the wireless performance in your buildings, between floors, or even compare every single access point on campus. The graphic above shows channel utilization of 2,216 access points from greatest to lowest. The access points in dark red are using very high percentages of the wireless medium to keep up with demand. You can then view the packet failure rate on those highly utilized access points. This will quickly tell you which access points have (1) high utilization AND (2) high retransmission rates. Upgrading these access points to Wi-Fi 6 is a good investment. –Note that, depending on when you are reading this, you want to select to go back in time a few months to when your campus wireless network traffic was normal. February is a good month because it is after the winter holiday and before spring break.

Areas where mobile devices struggle  


In order to minimize battery consumption, mobile device Wi-Fi radios transmit at much lower power (15mW typical) than the transmit power for access points (100mW or more). Because of this, mobile devices often struggle to send data (uplink) even though the mobile device Wi-Fi signal strength indicator shows full power. This happens because the mobile device measures how it is receiving signal from the access point (downlink). This problem is often worse in certain areas of the campus because building materials vary and things like concrete and metal exacerbate this uplink weakness.  OFDMA in Wi-Fi 6 allows a mobile device to concentrate its transmission (the uplink) on a smaller radio channel for higher power. If that didn’t make sense, imagine how the nozzle on your garden hose concentrates the flow of water to give it more power. The result for Wi-Fi 6 is the ability of a low power device to transmit with much greater uplink signal quality, which can help penetrate (or bounce around) heavy walls and other obstacles. So how can you detect areas on campus where Wi-Fi clients are experiencing low-quality uplink?

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Go back to the AI/ML Trends and Insights and compare average client RSSI (Received Signal Strength Indicator) across all access point on your campus. This will tell you how each access point is receiving signal from the wireless clients. Access points with low averages should be selected for a Wi-Fi 6 upgrade.

Areas of high interference


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Interference is a difficult problem to diagnose in wireless networks because the symptoms of interference can vary. Users can experience long onboarding times, slow app performance, and difficulty connecting to the cloud. The good news is that the AI Network Analytics feature in Cisco DNA Center will automatically identify interference and alert you on the “Top 10 Issues” window, right on the front page of the dashboard.

So, if you have seen these alerts on your home screen, it would be a good idea to see if Wi-Fi 6 can help mitigate this interference. If you go to the AI/ML “Trends and Insights” menu you can sort access points based on levels of interference. This can give you a list of your worst offenders. Click on one of the access points and look for the “Intelligent Capture” tool at the top of the window. This tool uses your network access points to perform complex packet, frame, and spectrum analyses.

Inside of the Intelligent Capture window, click on spectrum analysis and watch as the software begins to monitor the wireless traffic for interference severity and duty cycle. The waves show you the channels where the interference is located and how this is affecting the duty cycle of that particular access point. This is a very comprehensive test that will scan all of the available wireless channels with traffic from your actual network at that location.

Intelligent Capture lets you drill down on this and identify the percentage of channel utilization for this access point, other access points, and even non-Wi-Fi interference. The image to the right is a screen capture from the output of a spectrum analysis at 2.4 GHz (I cut the screen to be able to enlarge the image). Channels 1 and 2 have high levels of interference but channels 3 and 4 do not. If you find that interference is limited to one or two of the Wi-Fi channels, you can configure your access point to operate outside of these channels. However, if the interference is running across all channels you have a great candidate for a Wi-Fi 6 upgrade. The OFDMA synchronization in Wi-Fi 6 will greatly minimize any self-interference (interference between your own network devices and access points), and your Wi-Fi 6 clients will be able to transmit on a more narrow, more powerful radio channel giving them added robustness against internal or external interference.

A mere 20 Mbps of M2M data can take almost half of your access point’s capacity!

The IoT small packet problem


IT teams that operate networks for manufacturing, process control, mining, and digital cities are quite familiar with the IoT small packet problem. It has long been a thorn in the side of Wi-Fi networks used for machine-to-machine (M2M) connectivity and video surveillance. The issue is that these types of communication use small payloads of data in high frequency. Most forms of M2M encapsulate their data in 64-Byte UDP packets, while most normal IP file transfers use larger 1,500-Byte packets. A Wi-Fi access point is limited in the number of packets per second (PPS) that the imbedded chipset can process.  Imagine a Wi-Fi chipset capable of processing 30,000 PPS. For normal 1,500-Byte data packets, this device is capable of transferring 360 Mbps (30,000*1500*8). But, for 64-Byte packets the maximum throughput drops to only 45 Mbps. More importantly, 20 Mbps of M2M data can take almost half of my access point’s capacity!

Cisco Wireless, Cisco DNA Center, IOT, Wi-Fi, Networking, Cisco Tutorial and Material, Cisco Exam Prep

Cisco Wireless, Cisco DNA Center, IOT, Wi-Fi, Networking, Cisco Tutorial and Material, Cisco Exam Prep

To find small packet problem areas in your campus network, begin by looking at the AI/ML “Trends and Insights” menu and sort access points based on “Traffic.” This will single out the busiest access points based on packet transfers. Like before, use the Intelligent Capture feature, but this time look at the frame counts and frame errors window (shown at left). Any access points with lots of traffic, high frame counts and high frame errors are great candidates for a Wi-Fi 6 upgrade.In the past Cisco has done many enhancements to overcome the limitations of typical Wi-Fi chipsets, like HDX and “Turbo Performance” in the Cisco Aironet 2700 and 3700 series access points for 802.11ac. This HDX technology along with the quad-core processors now available in new Wi-Fi 6 chipsets take packet capacity to a whole new level, and you can see this in the Cisco Catalyst 9100 access points and Cisco Meraki Wi-Fi 6 Access Points.

My goal with this blog was to show you the power of AI/ML in Cisco DNA Center and how it can locate some of the less obvious, but more critical opportunities for upgrading to Wi-Fi 6. The material may be a bit more technical than most of our blogs here at Cisco, so please feel free to comment below with any questions you may have.

Cisco DNA Assurance and AI Network Analytics are included in the Cisco DNA Advantage software.

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