Homer and Bart and WiFi

I find myself explaining layer 1 physical spectrum analysis quite a lot these days.

Spectrum Analysis is everywhere today. There is Cisco Spectrum Expert, and CleanAir (now the chip is installed in every Enterprise Cisco AP). There is also Metageek Chanalyzer, and of course Cisco Meraki has it built in.

Identifying the different signals can be quite important to a wireless engineer in their day-to-day job.

I wanted to write this blog entry to introduce you to two of the most common signals that can be seen in the 2.4GHz and 5GHz range: DSSS and OFDM. (DSSS is 2.4GHz only, whilst OFDM operates in 2.4GHz and 5GHz.

DSSS is the mode of operation of 802.11 Prime (DSSS), and of 802.11b (HR-DSSS). OFDM is the mode of operation of 802.11a (OFDM), 802.11g (ERP-OFDM), 802.11n(HT), and 802.11ac (VHT).

So, what is an easy way to identify and remember these signals?

Well, this is where Homer and Bart (two of my favorite Simpsons characters) come into play.

Let’s imagine that Homer and Bart are up to no good (quite a common occurrence for this pair), and for some reason they have decided to hide behind a wall. Now let’s further imagine this wall is not quite tall enough to fully hide them, thus their heads are visible…

What you get is something like we see in Diagram 1

A cartoon of homer simpson and bart simpson on a graph.

DIAGRAM 1

In Diagram 1, we see two shapes, one that looks like Homer, and one that looks like Bart. Homer is effectively the shape of a DSSS transmission, and Bart is the shape of an OFDM transmission. There you have it! Easy to remember spectrum analysis.

So, taking a look at Diagram 2 below, we see again two shapes. At channel 6 we see a DSSS transmission, and at channel 11 we see an OFDM transmission.

A computer screen shows a graph that says real time fft

DIAGRAM 2: Actual Spectrum Expert Capture

 

Frequently people ask me, “Is that a “b” AP at channel 6, and a “g” AP at channel 11?” This is very important to stop and think about. These shapes actually show a “b” (or 802.11 Prime) DSSS transmission at channel 6, and a “g” ERP-OFDM transmission at channel 11. There is a lot of other information to take into account, but that is beyond the scope and intent of this article. This will be addressed in a different blog entry.

The take away is that, at channel 6, there was a “b” (or Prime) DSSS transmission and, at channel 11, there was a “g” ERP-OFDM transmission. Does that mean the AP at channel 6 is a “b” AP? Does it mean the AP at channel 6 was talking to a “b” client? The answer to both of these is maybe! All we know for sure is that there was a “b/Prime” DSSS transmission that we caught on channel 6, it could be a “b/Prime” (DSSS) AP, it could be a “g” (ERP-OFDM) AP talking to a “b/Prime” client, or it could simply be a “g” (ERP-OFDM) AP transmitting a Beacon at its lowest Basic/Mandatory speed – 1Mbps (802.11 Prime speed) that is sent out using DSSS.
So happy hunting for the “Homers” and “Barts”, and we’ll see you next month!

 

 

Blog Update Jun 2018

We all know Ekahau works really well with MetaGeek Chanalyzer, but what you may not know is the super-duper Ekahau SideKick seems to be taking over as a Spectrum Analyzer of choice, in its own right.

Will be doing more blog information on the SideKick soon…

(BTW, that last entry is from Wlan Professionals. Wlan Professionals is great community to get involved with, and is run by Keith Parsons, who is a legend in the WiFi community. They have blogs, podcasts and videos that are a great source of information. They also run great conferences throughout the year, one in the US and one in Europe. I try to attend WlanPros, Phoenix (US), every year.)

 

If you are looking to make your mark in the IT Industry, then NC-Expert offers excellent training courses aimed at relevant IT industry certifications – contact us today to get started.

NC-Expert Blog

Entry to Expert: How Wireless Certifications Accelerate IT Careers

By Admin • February 2, 2026
In today’s fast-evolving IT landscape, professionals who continuously expand their technical capabilities stand out in increasingly competitive promotions and job markets. Among the areas experiencing explosive growth, wireless networking has emerged as a cornerstone of modern infrastructure. From enterprise Wi-Fi deployments, to mission-critical IoT systems, and pervasive mobile connectivity, wireless skills are now indispensable for ambitious IT engineers. Earning certifications in wireless networking doesn’t just validate your knowledge, it catalyzes your career progression by opening doors to higher-level roles, deeper specialization, and accelerated professional recognition. In this blog, we’ll explore how wireless certifications, especially those from CWNP and CompTIA, help IT engineers develop from fundamental understanding to true experts in wireless technologies. Why Wireless Expertise Matters for IT Engineers Empty heading Wireless networks are no longer optional; they’re essential. Modern enterprises rely on Wi-Fi for daily operations in offices, retail environments, hospitals, campuses, and logistics centers. Technologies like Wi-Fi 6E and Wi-Fi 7 are pushing performance and reliability to new heights, while trends such as IoT, industrial automation, and edge computing broaden the scope of wireless connectivity. This rapid growth has created a global demand for professionals who can design, secure, troubleshoot, and optimize wireless networks. As organizations prioritize mobility, reduce hardware overheads, apply digital transformation initiatives, and implement high-density connectivity, engineers equipped with wireless expertise are increasingly valuable. Certified professionals not only understand the theory but can apply it in real-world environments: a difference that employers are willing to reward with better roles, more responsibilities, and higher compensation.

Wi-Fi 7 in 2025: Adoption, Real-World Impact, and What’s Next

By Rie • January 5, 2026
For more than two decades, Wi-Fi has quietly evolved from a convenience technology into a mission-critical utility. Now we’re in 2026, we can look back at 2025 and review wireless connectivity which underpinned nearly every digital experience: from enterprise productivity and cloud services to healthcare, education, retail, manufacturing, and smart infrastructure. Against this backdrop, Wi-Fi 7 (IEEE 802.11be) has emerged as the most ambitious leap forward yet. But as with every new wireless generation, the real story of Wi-Fi 7 in 2025 was not just about theoretical speeds or marketing headlines. It was about adoption, operational reality, and practical impact, and what IT engineers needed to understand as networks transitioned from Wi-Fi 6/6E into the next era.

Top 10 Wi-Fi Skills Sought by Employers - and How CWNP Training Delivers Them

By Admin • December 5, 2025
Nice to Have vs. Essential Empty heading Empty heading Wireless networking is no longer a “nice to have” skill... it’s mission-critical. From healthcare and education to enterprise, manufacturing, and public safety, organizations depend on reliable, secure, and high-performing Wi-Fi. As a result, employers are looking for professionals who don’t just know Wi-Fi, but understand how to design, deploy, secure, and troubleshoot it effectively. Empty heading pty heading So, what specific skills are employers looking for, and how can professionals demonstrate they have them?  Below are the top 10 Wi-Fi skills in demand today, and how CWNP® (Certified Wireless Network Professional) training helps deliver each one.