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Interference Detection and Mitigation with Cisco CleanAir

The previous blog on CleanAir went in depth on how MSE uses CleanAir information to locate interferers and the impact zone for each interferer. This blog takes a step back and gives an overview of the CleanAir technology.

How Interference Affects Your WiFi

802.11 devices operate in the 2.4GHz and 5GHz unlicensed bands. These are unregulated and experimental bands. As such, there are way more non-802.11 devices, including but not limited to cordless phones, video cameras, microwave ovens, Bluetooth headsets, DECT phones and even X-Boxes. Now even more devices are coming out that emit in these bands. These devices interfere with your WiFi network since they don’t work cooperatively with 802.11 devices, causing reduced network capacity and coverage, poor quality of voice and video, and link failures.

When an 802.11 device is ready to transmit and it senses interference, it will hold off transmission until it is finished.  If it is in the middle of a transmission where it has sent a packet and never receives an acknowledgement, then it will try to send the packet again. Issues like these  impact the throughput and capacity of your Wireless Network. An interferer like a microwave oven, which emits interference on a 50% Duty Cycle, will reduce the throughput by 50 percent. In the case of an interferer like a video camera, which emits interference at 100% Duty Cycle, when seen at Access Point above CCA threshold will stop the Access Point from beaconing. Due to this clients will not attempt to associate. Read More »

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Metageek Chanalyzer Pro + Cisco CleanAir = Powerful RF Visualization

As I partake in Cisco Live! activities, I wonder how the network team handles the thousands of geeks with their 3-4 geek toys each connecting to Wi-Fi from anywhere around the convention center.  I know a thing or two about how they went about planning, but hey, there is always Murphy’s Law that creeps up and nothing (always) works as planned…surprise surprise… think about the size of this conference and the World of Solutions (trade show floor) where so many of the partners want to show off their latest and greatest capability by setting up their own network. BAM: you have interference of all kinds all over the place. It’s a good thing the AP’s that are deployed have Cisco CleanAir® Technology to automatically classify and mitigates the interference. But wouldn’t it be great to be able to visualize the interference and the RF?

Enter visualization and Metageek.

It doesn’t take long for someone in the wireless industry to know that Metageek’s geeks know a thing or two about giving sizzle to RF and packets. We’ve certainly been around long enough, so that’s why we’ve been working with Metageek to cook up the Chanalyzer Pro with Cisco CleanAir® , the industry’s most advanced spectrum intelligence technology with the industry’s most visually captivating and comprehensive RF analysis tool. Perhaps you caught yesterday’s press release?

metageek Read More »

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Harsh Wireless Environment? Not a Problem.

It’s a fact – everyone wants wireless access.  Recent research indicates that by 2015, more US internet users will be accessing the internet over their mobile devices than on traditional computers.   With that many people online and on their mobile devices not having stable, secure wireless access is surely an impediment for companies as well as every day users. Companies leverage mobile devices to enable a more efficient workforce. Mobile devices are used to leverage “always-on” applications, increasing access for employees and as a better means of time management. Both of which increase employee productivity.  Companies also often rely on their wireless network for regulating employee safety.  Such is the case for the iron manufacturing company, North American Hoganas Inc.

With 11 production facilities across four continents in eight countries including the United States, where it staffs 250 employees, North American Hoganas Inc. needed to deploy an end-to-end wireless network in order to keep up with market demands and target new operational efficiencies.  Up to the minute communication is vital not only for business operations, but also for the safety of their plant employees.  Updating employees on risk assessments, proper product handling techniques, and work schedules are just some examples of mission-critical, daily communication from management to employees.  There was one problem that stood between North American Hoganas Inc and a successfully deploying a pervasive wireless network: North American Hoganas Inc. itself.

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Check your Spectrum!

October 3, 2011 at 10:28 am PST

Lately I had been spending a lot of time in the office rather than on the road.  Which isn’t all bad, as it gives me some semblance of a routine rather than living out of a suitcase.   It has also has given me some spare time to come up with another blog topic, which actually stems from some of the work I have been doing for customers lately.

Typically when a site survey is being done, we will do spectrum analysis work as well, part of my job entails creating and reviewing documents from this work, prior to delivering them to customers, which means I have been watching a lot of  spectrum analysis lately.   Most of the customers I have worked with recently have been with CleanAir APs, so they will be able to monitor their environment in real time, once the WLAN is up and running.  However it’s always a good idea to perform some spectral analysis while you are walking around doing a site survey.  And really why not?  If you are there and you have a few minutes, fire up the old spectrum card and get a capture of whats going on with your RF.   This helps make sure there aren’t any major layer 1 surprises when you go to install the new WLAN.  It doesn’t mean things won’t change, and they often will, due to the dynamic nature of RF.  It’s an ever changing environment, so what wasn’t there on Monday, might show up on Tuesday and be gone again by Wednesday.

Before jumping into particular types of interferes let’s talk about some of the data that Cisco Spectrum Expert can show you.  Two of the things I like to look at when looking at the RF in Cisco Spectrum Expert, are Real Time FFT and Duty Cycle plots, as pictured below.

The Real Time FFT is showing you is the RF energy in real time measured in dBm, so how loud or quiet the device is.  The next is the FFT Duty Cycle, which simply put it’s how utilized the RF is. Let’s say you have a device that is being captured as having a 1% duty cycle.  This means it’s using a very small amount of the available ‘air time’ to transmit its data.  Conversly if there is a device that is showing a 100% duty cycle it is using up all the ‘air time’ and not allowing other devices to use the RF medium to transmit.

Two other views I find helpful are the Spectrogram views.  These display the same info as the plots above, but are plotted out over time.  I use them in a few of the examples below.

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