Data rate vs. throughput is an important consideration when evaluating Ethernet radios.
Data rate is the total amount of data that can be transmitted from one radio to the other, but it only tells part of the story.
The meat of the story is represented by a radio’s throughput – the amount of your information that can actually be transmitted by the radio.
The difference between data rate and throughput is based on how radio transmissions work. Your information doesn’t just fly through the sky on its own. There’s overhead that takes up some of the data rate, such as turning the radio on, modulating the information, demodulating it at the other end and passing it to the next radio.
Each block of data is transmitted via a packet that also takes up some of the data rate. The packet provides security, as well as information on where the information came from and other details.
A Material Difference
Imagine that the data rate is a road – the packet is a truck driving over the road, and your information is the payload carried by that truck. Even if the road is rated to carry 1,000 tons of weight, that doesn’t mean your payload can weigh 1,000 tons – you need to subtract the weight of the truck from the road’s weight limit to know how large of a payload can be carried.
Other factors that affect throughput include the mode of transmission – router and client modes are more efficient than bridging and can deliver 10% to 20% higher efficiency.
Once everything is accounted for, you can use a 2:1 ratio to estimate your potential throughput. For instance, if a radio’s data rate is 300 Mbps, you can expect a throughput of around 150 Mbps. Your mileage may vary, of course, depending on the mode and level of security, among other factors. The 2:1 ratio can be considered a worst-case scenario.
Designed for Accuracy
The difference between data rate and throughput is so important that we’ve even developed our RF design utility to provide throughput figures to help our customers get the clearest understanding possible of what a specific radio can deliver.
When you’re in the market for new Ethernet radios, make sure you’re comparing apples to apples as you review your options. If it’s not clear, ask the vendor whether the specifications they’re providing include data rate or throughput. The answer can make a crucial difference in your network’s actual performance.