In recent years, studies of ad-hoc networks in which a plurality of wireless communication apparatuses (hereinafter, referred to as node apparatuses) connect to each other in an autonomously distributed manner have been carried out. Each of the node apparatuses of an ad-hoc network independently establish a network according to the communication environment.
Specifically, in the ad-hoc network, no access points are provided, and each of the node apparatuses relays to another adjacent node apparatus a data frame received from a node apparatus that is adjacent to it (hereinafter, referred to as an adjacent node apparatus) on the basis of the network topology, to transmit the data frame to the destination node apparatus. At this time, each of the node apparatuses transmits the data frame by selecting a path with a better transmission quality.
Because the network environment changes from to time, even when each of the node apparatuses transmits the frame on the basis of the network topology, the frame is not always transmitted to its destination node apparatus.
For example, even when the transmission of the data frame from a node apparatus to an adjacent node apparatus has been successful, for a certain reason (for example, a communication failure), an ACK (ACKnowledgment) frame sent back from the adjacent node apparatus may be missing.
In this case, the node apparatus that has transmitted the data frame determines that the transmission of the data frame has failed, and it re-transmits the data frame to another adjacent node apparatus. As a result, a plurality of the same data frames (hereinafter, referred to as overlapped data) are transmitted through the network. Therefore, the detection of overlapped data is very important.
As a technique related to the ad-hoc network, a method to detect whether or not the node apparatus has received the same data frame as a data frame received previously has been known.    Japanese Laid-open Patent Publication No. 2007-19574