SDR Course | Wireless Pi

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Learning about wireless communication is incomplete without sending any actual data over the air through a wireless channel. In this course, the fundamentals knowledge you gain from my book is complemented with a wireless communication project:

– See your own text and image fly through the air using a speaker (as a Tx) and a microphone (as a Rx)

Moreover, this course also covers the fundamental concepts of DSP and Software Defined Radio (SDR) without using any mathematics. Consequently, this is a summary of main ideas in relation to wireless communication systems from an SDR perspective.

Let us delve into more details below.

Rapid Skill Acquisition

Emphasizing on the most valuable stuff is crucial to learning any field. This is the key to rapid skill acquisition where we can go from 0.00 to 0.75 in a reasonably quick time. To understand this further, consider the following series.

\begin{equation*}<br>\frac{1}{2} + \frac{1}{4} + \frac{1}{8} + \frac{1}{16} + \cdots = 1<br>\end{equation*}<br>Now let us draw this series in a diagram.

I want to bring your attention to the following points.

The same concept is much easier to understand from the above diagram as compared to the equation. While a mathematician would rightly argue that this is not a rigorous proof, it serves our purpose well.

Even though 1/2 + 1/4, the shaded part in the diagram, does not become 1, it covers a substantial part of the whole. Similarly, from watching these videos and doing the provided GNU Radio exercises, you will gain an expert working knowledge of the subject that can be acquired within a reasonable time.

How exactly do I help here?

In old days, the information was scarce and we needed to learn everything, regardless of where it was coming from. In the past few decades, particularly with the rise of wireless connectivity and Internet, we have far more information than we can handle and the target should be to save our time and energy by separating the important from the unimportant. This is where I help the viewer by focusing on the main ideas.

Learning = Information + Activity

You might think that if you can read the book and understand all the concepts, what is the advantage of watching the videos and doing the GNU Radio exercises. Below I describe the main issue with most online courses and how this course solves that problem.

At its core, learning anything involves two parts: (a) information, and (b) activity. A simple act of walking or climbing to the top of any stairs is very difficult by committing only one leg to this task. Similarly, the first step towards expertise is acquiring information through books, people and online resources. The second step is doing the activity. Then, continue the cycle.

Information → activity → more information → more activity, ……

Some experts refer to this as the Input + Output cycle of our minds. In our context, these two parts are: (a) knowledge of communications and DSP algorithms, and (b) building (in fact, coding) the software defined radios.

To complement the knowledge part from the video lectures, this course provides several GNU Radio Companion (GRC) exercises for you to play with and learn about wireless communications by walking the path yourself. An example screenshot of a flowgraph is shown below (click on the image to enlarge it). For some built-in blocks, I explain the logic behind C++ code and relate them to the DSP algorithms explained in the lecture.

Wireless Transmission

Finally, we modify a GNU Radio example to build a real OFDM system that sends a text and image file over the air. Since SDR hardware is usually expensive, we utilize a USB sound card to transmit and receive through the speakers and microphone, respectively. See a short demo of the received signal in a wireless setting below.

See the input and output image files below for an audio loopback cable and for the wireless transfer through the speakers/microphone combination.

Most importantly, you will become able to visualize the amazing world of signals that lies underneath the seemingly simple process of bits sent and bits received. A short demo based on the above flowgraph is shown below. See the signals come alive!

Target Audience

In light of the above, this course is more suited to the following audiences.

Telecommunication professionals interested in gaining hands-on knowledge of what exactly goes on in the physical (PHY) layer of a wireless network (this bridging of the gap between academic concepts and industrial practices proves even more valuable if your ultimate target is a good job in the wireless industry)

Radio hobbyists who have played with communication systems but lack an understanding of what lies under the hood

Programmers and hackers who want to speak the language of the machines by writing programs that make their words fly in the air

Curious people looking to expand their knowledge outside their areas of specialization

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