How Does the MCS Index Work?

The MCS index reveals specific issues, but it can often be too complicated to use on its own. Learn how the 7MCS Wi-Fi experience score from 7SIGNAL bridges the gap.

Key takeaways:

• The Modulation Coding Scheme (MCS) index helps engineers understand data rates and evaluates the RF environment.
• MCS is more effective than simply assessing signal strength because it shows actual performance for a client, and it’s easier to compare device experiences across a network.
• 7SIGNAL created the 7MCS Wi-Fi experience score to make the MCS simpler to understand and use.

Assessing Wi-Fi performance and finding the root causes of issues are crucial tasks. And the Modulation Coding Scheme (MCS) index is one resource that lists each possible combination of modulation type, coding rate, and the number of spatial streams, delivering valuable information about data rates for each Wi-Fi protocol. 

However, it’s not always simple for IT staff and engineers to understand the MCS index, as it’s is a complex chart of parameters and numbers. This is why 7SIGNAL created the much simpler 7MCS Wi-Fi experience score, which adjusts values, so they're not specific to a number of spatial streams. 

This guide walks through the MCS index, how it helps break down Wi-Fi issues, and how that’s easier with the 7MCS Wi-Fi experience score from 7SIGNAL. 

What is the MCS index?

The MCS index measures a Wi-Fi connection based on various factors that exist between an end-user device and an access point. It essentially assesses the quality of a radio frequency (RF) environment.

The MCS index breaks down the data rates in 802.11 protocols, including details like the modulation type and coding rate for each specification, such as channel width, spatial stream, and guard interval. Let’s dig into what some of these terms mean:

• Modulation: Modulation uses      amplitude and phase to encode information onto a carrier wave. Lower data rate modulation has more of a difference between symbols, while higher data rate modulation has symbols that are closer together. The former results in more error protection and a better Wi-Fi connection, whereas higher data rate modulation leads to a more fragile connection.
• Coding rate: The number of bits required to send a certain number of bits, or how many bits transfer data and how many correct errors.
• Channel width: Channels with more width can attain higher bandwidth, but a wider channel could mean more noise.
• Spatial streams: The number of data streams being used. More streams mean higher data rates but can be more susceptible to interference.
• Guard interval: The pause or space between symbols being transmitted. More packets can get through with a shorter guard interval, but there may be more opportunity for interference.

When all of these connection parameters are defined, engineers can look up what the data rate will be between two stations on the MCS table for the applicable Wi-Fi generation (e.g., 802.11ac). The index thus helps Wi-Fi professionals understand data rates and references all of this information in one table.

How the MCS index helps resolve wi-fi issues

Many IT professionals and engineers may first be tempted to focus on signal strength to see how a connection is performing. But that measure alone just isn’t consistent across Wi-Fi clients     , which is especially challenging when you’re dealing with lots of different client devices on the Wi-Fi. Instead, the MCS index dives deeper into what’s going on with a connection.

The index reveals the actual performance of the Wi-Fi from the perspective of one client. For example, when a client is trying to use a high data rate, the MCS shows what a client is actually able to accomplish. When the MCS score is low (under 4), that means a client is having issues because of radio frequency challenges. This result immediately shows engineers an underlying problem they need to deal with to create a better experience.

The MCS index also makes it easier to compare how the Wi-Fi performs on different devices at a given time. It abstracts away the differing      capabilities of the various clients, including the number of spatial streams, which can bring engineers key connection information. The index demonstrates the actual station performance that can be compared across end-user devices.

Why 7SIGNAL invented the 7MCS Wi-Fi experience score

The MCS index reveals data that helps engineers view how the Wi-Fi is performing for devices, but many clients don’t make their MCS value available, and the MCS values between Wi-Fi generations are not consistent     . That's why 7SIGNAL created the 7MCS Wi-Fi experience score.

This score can be used on macOS, Windows, Linux, and soon Android as well     . And the 7MCS breaks everything down and changes the MCS values, so they're not specific to a number of spatial streams. These scores can be compared across Wi-Fi generations from 802.11n to 802.11ax.

These changes allow engineers to view the 7MCS score as a simple “quality of Wi-Fi experience” scale, and it provides instant information about performance so they can keep improving the environment.

The 7MCS Wi-Fi experience score is found within the Mobile Eye®, 7SIGNAL’s Wi-Fi performance agent for mobile devices. This platform, along with our other wireless experience monitoring solutions, helps you track performance from the end-user’s perspective, so you can stay proactive in preventing and addressing issues.

7SIGNAL® is the leader in wireless experience monitoring, providing insight into wireless networks and control over Wi-Fi performance so businesses and organizations can thrive. Our cloud-based wireless network monitoring platform continually tests and measures Wi-Fi performance at the edges of the network, enabling fast solutions to digital experience issues and stronger connections for mission-critical users, devices, and applications. Learn more at www.7signal.com.