CPU Contribution. For both dual-core smartphones, CPU consumes
a significant amount of energy. Figure 5(b) plots the CDF
of the normalized CPU energy cost over all the measurement instances.
We mix the results of the two smartphones since they
are similar. Overall, the median value is 20% for LTE-only and MPTCP, 23% for Bundling, and rises to 60% for WiFi-only, while
the maximum value can reach 80% for WiFi-only. To the best of
our knowledge, this is the first field measurement over many locations
that shows data transfers can consume significant CPU energy,
using popular multi-core smartphones. More importantly, our
result shows that an accurate energy model must not ignore the
CPU contribution.