The world is becoming increasingly aware of 5G as it is rolled out across the globe in 2020. As the fifth generation of cellular technology, 5G touts increased speed and connectivity, promising to connect people and devices to each other more than ever before. One of the key components that is consistently quoted regarding the availability of 5G is “low latency”. But what does that actually mean? We’re going to cover the meaning of latency, technologies responsible for improved latency in 5G, and what industries actually rely on low latency.
What is latency?
Latency is a measurement of time between an action and a response. In computing, latency is usually described as the amount of time between making a request (clicking something on a website) and receiving a response (seeing the page fully loaded). You usually see latency mentioned regarding gaming, websites, and business applications.
Companies invest considerable sums of money to achieve lower latency. High latency can negatively affect their bottom line if a website loads too slowly or a streaming application isn’t smooth. This usually comes in the form of CDNs, caching, or other various methods that physically route the request to a server closer to the requestor (client) or make copies of the data available that reduce the querying time.
Latency and 5G
Regarding 5G, latency is the amount of time it takes for information to travel from the cell tower to a receiver, such as a cell phone or vehicle. This is not to be confused with bandwidth. Bandwidth is the maximum amount of data that can be transferred over a network at a given time. Latency is a function of only time.
Earlier cellular technologies, such as 4G, are physically constrained at how fast they can transfer data. One of the primary reasons 5G is an enhancement from the previous generations is the ability to support lower latency. This comes via technological improvements in how fast the data is physically transferred. This singular piece is what ultimately allows many of the improvements to industry that 5G promises, such as mission critical services and autonomous vehicles. More on that below.
Technological improvements that support lower latency
Cellular communication, like WiFi, FM radio, and other technologies, are carried over radio frequency waves. Waves are measured by their frequency and length, with frequency measured in hertz (cycles per second) and wavelength measured in meters. Radio waves travel at the speed of light in a vacuum, and close to that on Earth after considering interference. But since radio waves all travel at [almost] the speed of light, how can 5G claim to support 1 millisecond latency while existing technologies such as 4G LTE average 40ms?
The difference is in the scheduling unit of the waves while waves are not traveling. Consider a subway that is on a one-minute schedule. Every minute, a train with ten cars arrives, picks up passengers, and carries them to the next destination. But, what if you’re ready after only three seconds, and could hop in just one freestanding subway car on an adjacent track? Same speed, but more flexible scheduling.
With radio waves, a frame has a 10ms length and is divided into 10 subframes, all with 1ms length. 4G LTE is limited to communication via one subframe. This means that a duration of 1ms is consumed solely for transmitting the block via air interface. This is also excluding device processing time. 5G leverages a new technology, referred to as “mini-slotting” which allows signals to be sent in six separate slot configurations within the standard 1ms subframe. This means that the size of a transport block could be as small as 0.03125ms. Like taking a single subway car rather than waiting for the entire train, 5G leverages these smaller slot configurations.
What this means for industry
Now that we understand latency, let’s take a look at the real world application. While lower latency may mean a faster rendering of a YouTube video, that only scratches the surface of what becomes available with 1ms latency.
For the first time ever, the world will be connected at almost real-time. This means that technologies that could not physically exist before will now become the new norm. Response times will be fast enough for autonomous vehicles to be functional. Mission critical services such as energy grids and first responder aid as well as VR and remote surgeries will become practical.
Lower latency is one of the key contributors to the speed and availability of 5G. With a new framework that supports more flexible scheduling, latency will be reduced significantly. This opens the world to an entirely new level of connectivity.