Patent ID: 7953571

Claim:
A sensor network system comprising: a sensor terminal, which alternates between an activated state and a sleeping state, collects and transmits observation data by wireless communications in said activated state and stops collecting and transmitting observation data in said sleeping state; and a management server, which includes: a latest data storage manager which manages a set of latest observation data of observation data received from said sensor terminal; a history data storage manager which manages history data of the observation data received from said sensor terminal from a set of previous observation data received from said sensor terminal to said set of latest observation data; and a missing data manager which manages loss of said history data indicating missing observation data transmitted from said sensor terminal and not received by said management server, wherein said missing data manager sends a retransmission request to said sensor terminal to retransmit the missing observation data that was not received by said management server based on a predetermined rule, wherein said sensor terminal, upon receiving said retransmission request from said management server, retransmits said missing observation data to said management server, and wherein, in case that a request for observation data is received from user terminal, at least one of the set of latest observation data managed by said latest data storage manager and the history data managed by said history data storage manager is output to said user terminal according to a type of said request for observation data received from said user terminal.