Monday, July 13, 2015

Packet Loss is Chief Experience Degrader on Mobile Networks

Traditional network “quality” metrics are based on throughput and latency. But according to a study by Kwicr, the chief source of mobile app quality problems now are packet loss and throughput variation.

Throughput and latency matter, but only to a lesser extent, in the mobile environment.

In part, that is because mobile video has emerged as a key app, and mobile video and mobile audio are affected by both packet loss and throughput variation.

But devices matter as well, in particular older devices with slower processors and less available memory. Additionally, older devices may only support more crowded 2.4GHz Wi-Fi bands, or not be enabled with the fastest cellular technologies such as LTE and LTE Advanced.

Both types of impairments result in stalls and lower quality streaming, even if there is ample bandwidth to service the customer.

Kwicr says content delivery networks are effective ways to improve app performance, particularly for apps with cacheable content such as streaming video, streaming audio, and static web page content.

That is a logical observation for a company that sells a mobile content delivery network.

The main point, Kwicr argues,  is that mobile Internet access networks are different from fixed Internet access networks.

TCP performs exceptionally well with wired networks, because packets are lost only when the network is congested, Kwicr says.

TCP is designed to work with wired networks and equitably split bandwidth across the applications that are utilizing the fixed sized links on these networks.

Mobile broadband is characterized by quickly varying available bandwidth, caused by impacted by endpoint motion, weather, topographic feature interference (mountains and buildings), the active or passive coordination between multiple access points or base stations, and contention for spectrum.

All that leads to a rapidly-changing bandwidth environment, something TCP was not designed to anticipate.

“Our data indicates that the throughput available to a mobile app for download and upload varies greatly during a single app session,” said Kwicr.

Wi-Fi and Long Term Evolution (4G) have the highest average throughput, but Wi-Fi has unusually high rates of packet loss events.

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