Home Analysis Human eye puts strain on Wi-Fi

Human eye puts strain on Wi-Fi

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By Bülent Çelebi, Chairman and Co-Founder, AirTies Wireless Networks

The human eye is capable of resolving even finer resolutions and colour shades than had been thought, according to various recent studies. This is good news for most of us and certainly for consumer electronics makers purveying 4K TVs and other devices, since it is now clear that we truly can tell the difference. The findings may be less welcome for providers of network services who have to come up with the bandwidth to deliver content at ever higher resolutions. It is also going to increase the pressure on Wi-Fi, which already often struggles to meet QoS expectations for normal HD video at resolutions up to 1920 x 1080 pixels per screen. Wi Fi, as we know, is fast emerging as the final carrier of broadband services to the end device, the so called “last nine yards”, and will increasingly serve main screen TVs as HDMI dongles take off. 

A key point though, harping back to these studies of human vision, is that it is not just big screens that will be receiving video in 4K. It will also be tablets, laptops, gaming consoles and even large screen smartphones. This point was made recently by wireless semiconductor company Quantenna, arguing that Wi-Fi needed to become 4K capable and that it was makers of mobile devices like tablets that were leading the charge. Quantenna cited a study finding that even on 10-inch tablets 4K really did make a difference, precisely because the human eye can resolve details at smaller scales than had previously been thought.

In any case, people view tablets from close up from at most a metre and usually half that. So although individual pixels are smaller on a tablet than a big TV they appear as the same size to the viewer from close up, which means that the total number of pixels on the screen needs to be about the same for a given quality of experience. The relevant measure of resolution for a tablet is the pixel density per inch (PPI) and the research cited by Quantenna found that the average person can detect the difference in quality up to a PPI level of 344 and 573 for somebody with perfect vision. 

This is where things get interesting, for on paper so called full HD at 1080 x 1920 should be good enough on tablets and smartphones for most people, since it equates to a PPI of 508, well above the level for normal vision. But anecdotal evidence had suggested otherwise, so Sharp Devices Europe decided to conduct detailed experiments on a sample of 50 individuals viewing a variety of images at different resolutions. It turned out most people could resolve detail way beyond the expected PPI levels, up to well above 1000. 4K equates to 1016 PPI, so the study indicated that people could detect even the further improvement yielded by 8K, which doubles the pixel density again. 

The explanation is that the human visual cortex can detect alignment between geometric structures such as lines at very small scales even when the eye cannot resolve individual pixels. It does this by processing multiple image points simultaneously along a line.

While oculists ponder the exact visual processes involved such findings are likely to boost 4K and encourage CE makers to accelerate product developments in their quest for higher profits than they can get from normal HD models. At the forthcoming CES 2015 in Las Vegas all the usual suspects, such as Samsung, LG and Sony, will be lining up not just with big screens but also smartphones and tablets boasting higher resolutions than ever before.  There will be some 8K models too and vendors will be able to highlight this research indicating that this is not a step beyond human visual perception, even on small screens. 

We will be there as well, explaining that Wi-Fi armed with the right technology will be able to cope with 4K and even 8K if necessary and that in the overwhelming majority of homes there will be no need for the assistance of a wired backbone.


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