How latency affects the mobile experience
A time-honoured trick used by humourists and comedians involves the principle of delayed reaction.
‘My dog’s got no nose.’
‘How does he smell?’
A long silence follows, while the audience grow increasingly expectant.
‘Awful.’
The punchline is dreadful, but the delay heightens its impact, providing a rare example of a pregnant pause actually being beneficial.
In most other respects, unexpected pauses are a hindrance – and nowhere more so than when using mobile devices.
Here, split-second response times can be crucial for a smooth and productive online experience.
It’s fine to wait a few seconds while Twitter loads, but you can’t realistically wait a few seconds for FIFA 21 to process your attempt at a bicycle kick.
Such pauses and stutters are often caused by something called latency. But what is latency, and how does it impact on the mobile experience?
What is latency caused by?
Latency is defined as the delay between a device issuing a query and receiving a response.
That might be the time it takes a webpage request to display a result, or the time it takes for an in-game instruction to be processed.
When you click a link, hit Enter or issue a command, an instruction has to be sent from your device to the server hosting whatever app, game, website or service you’re presently accessing.
The server has to interpret your instruction, issue a response, and deliver it to your device.
The time this takes is measured in thousandths of a second, or milliseconds.
What is latency going to do to my device’s performance?
In essence, latency causes stuttering and unresponsive user experiences.
You might notice it while waiting for a webpage to load from a foreign server, where data has to travel halfway around the world and back every time you issue an instruction.
Microsoft and Oracle both believe latency over 50ms should be avoided for database access, such as customers choosing items on an ecommerce website.
Latency of 100ms would make many online games unplayable, with other things happening in the meantime while people await their most recent instruction being actioned.
On a video call, latency of 150ms causes freezing and dropouts, with audio and video potentially going out of synch.
It’s latency that causes live footage to pixelate or sound echoey, as devices reduce their picture and sound quality to ensure at least something gets through.
This reveals the presence of adaptive bitrates – pieces of data are sent at the highest quality the connection can support at that instant.
Adaptive bitrates are one of many techniques hosting companies and service providers use to minimise latency.
Others include building global data centre networks with enough bandwidth to handle sudden data spikes, while clever routing protocols optimise data’s transit from server to screen.
The impending release of additional 5G bandwidth should further reduce mobile latency, providing smoother and more enjoyable online gaming, streaming and surfing.