The communication of wireless sensors is provided by a group of program modules called network stack. Figure 1 shows the network stack used in DOT3 wireless sensors. At the top level, an application sends andreceives data in a fixed-size packet. Then, the packet is fragmented to bytes in the media access control(MAC) layer which is implemented as ChannelMonC module. At the sender side, MAC layer prefixes a specialsequence of bytes called preamble to the data bytes so that the receiver side detects the beginning of a packetout of byte streams. At the receiver side, the radio chip forwards every data byte it receives to the MAClayer. If a sequence of bytes matches preamble, the MAC layer reads the fixed size of bytes and reassembles apacket. The received packet can be processed further in upper layers. For example, a packet can be checkedof its correctness using CRC (RFCommC module). The network stack can use forward error correction (FEC)to correct packet errors on transit. In this case, the data bytes are encoded after being fragmented at thesender side and the received bytes are decoded at the receiver side.