What is DSSS Data Encoding?

Passing secret codes back and forth is something we learn to do in elementary school, but as we level up our geek credentials, we keep finding cooler ways to secure our communications.

In 1942, a gentleman by the name of Gustav Guanella created a method for spread spectrum communications called DSSS. So, what is DSSS data encoding — and why is it used for wireless communications?

What is Spread Spectrum?

Before we explain DSSS data encoding, let’s explain spread spectrum. DSSS is a form of spread spectrum wireless communications, so we need to understand the basics first. 

Radio signals are subject to the laws of physics. For instance, low-frequency radio waves carry less information than high-frequency radio waves. Low-frequency radio waves penetrate physical objects easily while high-frequency waves are so delicate they bounce off raindrops. 

One of the ways we bend the laws of physics is by sending information on a wide range of frequencies. If we split data into pieces and send each piece at a different frequency, there’s a better chance a receiver will capture most of it. 

Here's how it fits together. We know we can send more data at higher frequencies, but higher frequencies tend to bounce off things. So instead of sending data at a single high frequency, we send data over a group of high frequencies at fast intervals. Even if some data is blocked, we’ll get most of it. This is how spread spectrum technology works. 

What is DSSS Data Encoding?

DSSS encoding improves how spread spectrum is utilized. When DSSS-encoded data is sent, the transmitter sending that data uses the entire spectrum to send data all at once. By not hopping between frequencies, we increase the available bandwidth. 

Spread spectrum is more resilient for data transmissions because there is a better chance we will receive most data sent to us. We may lose some, though. It’s like listening to FM radio. Occasionally, we’ll hear some static in the broadcast. 

DSSS encoding eliminates that noise. Before data is sent, DSSS encoding adds a bunch of pseudo noise to the data first. That pseudo noise is called chips. The radio transmitter and receiver use the same algorithm for adding and removing those chips to the original data. 

Ready to Learn More About Wireless Technology?

Did you notice how we kept calling it DSSS encoded data and not encrypted data? Why isn’t DSSS encoding considered encryption? There’s a lot to learn about DSSS encoding and wireless communications. 

That’s why studying for the Certified Wireless Network Administrator certification is so popular. Our CWNA online training can teach you the ins and outs of wireless communications — and how they apply to the world of network engineering. Sign up for a free 7-day trial today!

What is Barker 11?

There are variations of algorithms used to add and remove chips from wireless data. For instance, the Wi-Fi standard uses one called Barker 11. 

Barker 11 is simple. Each bit of data is broken down into 11 new bits. We use the pseudo-noise seed from Barker 11 to create values for those bits. Barker 11 always creates binary data (1 or 0). 

Let’s say the original bit equals 1 and Barker 11 uses a pseudo-noise seed value of 01001000111. The 11 new bits will be 101110111000. 

Notice how the DSSS encoded bits are opposite values of the pseudo-noise seed? Here’s how that works. We use a correlation for the value in the pseudo-noise seed against the value of the original bit of data:

• 1 and 1 = 0

• 1 and 0 = 1

• 0 and 1 = 1

• 0 and 0 = 0

So, given that our original bit value is 1, we have:

• 0 and 1 = 1

• 1 and 1 = 0

• 0 and 0 = 1

• Etc.

Why Does 22 MHz of Spectrum Matter?

For the 801.11 WiFi standard, we need 2 MHz of spectrum to send one bit of data. Because DSSS encoding is a form of spread spectrum, and we are sending 11 bits of data for each bit per Barker 11, we need 22 MHz of spectrum to transmit each bit. 

Does that number look familiar? Here’s why. One of the options available in most consumer router dashboards is how wide the WiFi channel it uses is. By adjusting the channel width, we can add more resiliency to our WiFi broadcast. 

Remember that we need 22 MHz to send all 11 bits of DSSS encoded data? If we use more than 22 MHZ, we can send more bits of DSSS encoded bits. 

Does DSSS Encoding Add Parity?

Barker 11 DSSS encoded data has parity built in. That’s why DSSS encoding is so resilient. 

If some of those 11 bits are lost in transmission, the radio receiver can still rebuild the original bit. In Barker 11 encoded data, the receiver only needs to receive 2 of those 11 bits at minimum to reconstruct data. The first bit is used to determine the original value, and the second bit is used to verify that value. 

The most amazing thing about DSSS encoding is that encoded wireless transmissions sound like white noise. It’s unintelligible static. To decode the transmission, you need to know what spectrum of frequencies data is being transmitted on and what DSSS encoding algorithm was used to encode that data. 

That’s awesome! So, with DSSS encoding, we get more resilient wireless communications with built-in parity that’s difficult to snoop on.