# Big Data Collection in Large-Scale Wireless Sensor Networks
## 3 Overview of Big Data
### Characterization of Big Data
#### 3.1.2 Velocity  
_Velocity_ refers to the dynamic and/or temporal aspect of the data, and their update and analysis time. Data are no longer processed and analyzed offline, but in real time or near-real time. They are produced in continuous streams, during which real-time decisions can be made. These are the data especially from sensors, requiring fast processing for a real-time reaction. In the case of such high-velocity data generating very large volumes, it is no longer possible to store them as they are, but only to analyze them in streaming, or even to summarize them; for instance, in time-sensitive processes like detecting frauds, Big Data must be used as they stream into industries in order to maximize their value. The challenge of Big Data applications is to recover data almost instantly, process them in real time, and extract useful information.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Source** & **Production** \\ \hline \hline \multirow{4}{*}{YouTube} & - Users upload 400 h of new videos each minute of every day. \\  & - Each month, more than 1 billion unique users have access to YouTube. \\  & - Users watch more than 4 million videos every minute. \\  & - Users watch 5.97 billion hours of videos each day. \\ \hline \multirow{4}{*}{Facebook} & - Users click the Like button on more than 4 million posts every minute. \\  & - Every day, 5.75 billion likes are registered. \\  & - Every day, 4.3 billion messages are posted. \\  & - 100 terrabytes of data are uploaded daily. \\  & - Over 2 billion monthly active users in 2017. \\  & - The site has been translated into 70 languages. \\ \hline \multirow{2}{*}{Twitter} & - 656 million tweets every day. \\  & - The site has over 355 million of active users per month. \\ \hline \multirow{3}{*}{Instagram} & - 7.1 million active users per month. \\  & - 34.7 billion shares of active photos per month. \\  & - 3.25 billion hours of video are watched in one month. \\ \hline \multirow{3}{*}{Foursquare} & - This site is used by 45 million of people worldwide. \\  & - This site receives over 5 billion check-ins per day. \\  & - Every minute, 571 new websites are launched. \\ \hline \multirow{2}{*}{Google+} & - 1 billion accounts have been created. \\ \hline \multirow{2}{*}{Google} & - The site had over 5.2 billion daily searches in 2017. \\  & - Every day, 25 petabytes are processed. \\ \hline \multirow{2}{*}{Apple} & - Approximately 47,000 applications are downloaded per minute. \\ \hline \multirow{2}{*}{Amazon} & - USD373 million in sales every day in 2017. \\ \hline LinkedIn & - 2.1 million groups have been created. \\ \hline \multirow{2}{*}{Email} & - Every day in 2017, 269 billion emails have been sent. \\ \hline \multirow{2}{*}{Mobile Device Data} & - In 2017, 8 exabytes of data have been created on mobile devices. \\  & - In 2017, there were 3.394 billion mobile Internet users. \\ \hline \multirow{2}{*}{Data created by the Internet of Things (IoT)} & - 2.5 quintillion bytes of data are created every day by mobile devices, \\  & WSNs, Smart TVs, cars, etc. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Volume of created data (Sources: bloomberg.com, IBM, BBC, onereach.com, Internet Live Stats, Internet World Stats, Forbes, Data Never Sleeps.).