Why Latency Matters to Mobile Backhaul - O3b Networks

Why Latency Matters to Mobile Backhaul
Interactive user services
The impact of latency on interactive services is more subjective. As the
delay increases, the applications continue to function. However, the sense
of immediacy and the usability degrades. At some point, the user becomes
less tolerant of waiting for the response, eventually giving up and moving
on to something more satisfying. A great deal of research has been done
by companies whose revenues are impacted when users abandon their
transactions.
The importance of latency on web commerce was first showcased by Zona
Research in 1999 with the popular “8-second rule”. Zona found that more
than $4 billion e-commerce sales were lost due to poor site performance,
which ultimately led to transaction abandonment. In a follow up study in
2006, Jupiter Research concluded that the threshold had been reduced to 4
seconds, as more users experience the performance of high-speed
broadband.
Google discovered that the number of web searches and ad revenue
declined as they increased the number of user search results from 10 to 30.
Further research found the result was due to the additional time required to
compute and present more results to the user. Increasing the results from
10 to 30 required an additional 500ms to compute and resulted in a 25%
drop in the number of searches done by users. Following this initial study,
Google performed additional tests focused exclusively on the latency. They
injected artificial delay into the display of the search results. An increase in
display time of 400ms actually decreased the number of searches per users
by 0.44% to 0.76%. While these drops in usage appear small, they had a
direct and meaningful impact on ad revenue.
Similarly with Amazon: “We tried delaying the page in increments of
100 milliseconds and found that even very small delays would result in
substantial and costly drops in revenue,” said researcher Greg Linden.
Linden provides a precise figure: -1% sales for 100ms or more latency.
(Greg Linden in “Make Data Useful”, Data Mining course Stanford in 2006).
Steve Souders from O’Reilly adds more examples in a blog posting
http://radar.oreilly.com/2009/07/velocity-making-your-site-fast.html.
In “Performance Related Changes and their User Impact,” Eric Schurman
(Bing) explains that Bing researchers have conducted tests adding a static
delay of 50 ms to 2 seconds to their servers. A negative impact on the Bing
performance indicators resulted as soon as the delay increased by more
than 50ms. The degradation noticed was linear.
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