  This chapter examines the possibility to analyze and compare human activities
in an urban environment based on the detection of mobile phone usage patterns.
Thanks to an unprecedented collection of counter data recording the number of
calls, SMS, and data transfers resolved both in time and space, we confirm the
connection between temporal activity profile and land usage in three global
cities: New York, London and Hong Kong. By comparing whole cities typical
patterns, we provide insights on how cultural, technological and economical
factors shape human dynamics. At a more local scale, we use clustering analysis
to identify locations with similar patterns within a city. Our research reveals
a universal structure of cities, with core financial centers all sharing
similar activity patterns and commercial or residential areas with more
city-specific patterns. These findings hint that as the economy becomes more
global, common patterns emerge in business areas of different cities across the
globe, while the impact of local conditions still remains recognizable on the
level of routine people activity.

Physics and Society;Computers and Society;Social and Information Networks;Data Analysis, Statistics and Probability