Let’s continue our discussion from the last lecture, diving deeper into frequency and wavelength. As a quick review, we talked about the electromagnetic spectrum, noting that Wi-Fi (802.11) operates in a specific part of this spectrum. We also covered waves as the medium used to transmit data from point A to point B and discussed two types of waves. Let’s now focus on frequency.

 

Understanding Frequency

Frequency is the rate at which a wave repeats. Think of it as the measure of how many times a wave cycle occurs within a certain period. Higher frequency means the wave cycles happen more frequently, while a lower frequency means the cycles occur less often.

To visualize this, consider Wi-Fi frequencies:

• 2.4 GHz: Here, the frequency is lower, so wave cycles happen less often.
• 5 GHz: With a higher frequency, wave cycles are more frequent.

On a 5 GHz frequency, for instance, you may have almost twice as many cycles as on the 2.4 GHz within the same time period. Higher frequencies like 5 GHz, however, face more obstacles in penetrating walls or other barriers compared to lower frequencies like 2.4 GHz. This is because lower frequencies can pass through these mediums more easily.

Frequency Units: The Role of Hertz

The unit of frequency is Hertz (Hz), named after physicist Heinrich Hertz, who proved the existence of electromagnetic waves. In wireless communication, we generally work with gigahertz (GHz), with Wi-Fi often operating at 2.4 and 5 GHz. Additionally, newer standards use 6 GHz, and 60 GHz is common for outdoor point-to-point links.

Now, consider this: if you set up a 60 GHz point-to-point link, will it cover a large distance? Given its high frequency, 60 GHz doesn’t penetrate mediums easily—even air can attenuate the signal. You might only reach 1 to 2 kilometers at most. Moreover, environmental conditions like rain or bad weather further limit signal reach at this high frequency, making it less suitable for countries with frequent rain. However, in places with mostly sunny weather, using 60 GHz can be beneficial due to the large bandwidth it offers.

 

Moving on to Wavelength

In the last part of this lecture, let’s discuss wavelength. A wavelength is the distance a wave travels to complete a full cycle. Picture this as one cycle going up, down, and back up again. Higher frequencies have shorter wavelengths, while lower frequencies have longer wavelengths.

For example:

• At 2.4 GHz, the wavelength is approximately 12.5 cm (or 4.92 inches).
• At 5 GHz, the wavelength shortens to about 6 cm (or 2.36 inches).

This difference explains why 2.4 GHz can cover a greater distance than 5 GHz; its longer wavelength allows it to reach further. In comparison, it takes nearly double the cycles at 5 GHz to reach the same distance covered by one cycle at 2.4 GHz.

Summary and Key Takeaways

We’ve discussed how frequency and wavelength affect wireless communication, particularly in terms of distance and penetration ability. When planning a setup, always choose the appropriate frequency for your scenario. For example, using 60 GHz in rainy regions is impractical, as high frequencies struggle to pass through rain. A lower frequency, with a longer wavelength, is much better suited in such cases.

That’s everything I wanted to cover in this lecture. We’ve now explored frequency and wavelengths in detail. I hope you found this informative, and I’ll see you in the next lecture!