Uncovering the Relationships Between Phone Communication Activities and Spatiotemporal Distribution of Mobile Phone Users

Abstract

In recent years, call detail records (CDRs) have been widely used to study various aspects of urban and human dynamics. One assumption implicitly made in many existing studies is that people’s phone communication activities could represent spatiotemporal distribution of the population, or at least of the mobile phone users. By using a mobile phone data set which consists of CDRs plus other cellphone-related logs (e.g., cellular handover and periodic location update), we derive two cellphone usage indicators (volume of calls/messages [$V$] and number of active phone users [$N$]) as well as the spatiotemporal distribution of mobile phone users, and evaluate their relationships through correlation and regression analysis. We find that the correlations between the number of mobile phone users and each of the two cellphone usage indicators remain high and stable during the day time and in early evening (i.e., 07:00–21:30). However, their relationships revealed by the regression models vary greatly throughout a day. Researchers therefore should be cautious when using mobile phone communication activities to quantify certain aspects of urban dynamics. Our regression analyses suggest that the log-transformation model performs better than the simple linear regression model (in predicting phone user distribution) when the independent variable ($V$ or $N$) is fixed. Also, we find that $N$ serves as a better independent variable than $V$, which is affected more by individual “burst” of phone communication activities, when explaining spatiotemporal distribution of mobile phone users. A 3-fold cross validation suggests that CDRs can be used along with other data sources (e.g., land use) to deliver more robust estimation of phone user distributions, which potentially facilitate dynamic projection of urban population distributions.