Wireless Ad Hoc and Sensor Networks

44 Wireless Ad Hoc and Sensor Networks(http://www.xbow.com/) makes three Mote processor radiomodule families — MICA (MPR300) (first generation), MICA2(MPR400) and MICA2-DOT (MPR500) (second generation).Nodes come with five sensors installed — temperature, light,acoustic (microphone), acceleration/seismic, and magnetic. Theseare especially suitable for surveillance networks for personnel andvehicles. Different sensors can be installed, if desired. Low powerand small physical size enable placement virtually anywhere.Because all sensor nodes in a network can act as base stations,the network can self-configure and has multihop routing capabilities.The operating frequency of the ISM band is either 916 MHzor 433 MHz, with a data rate of 40 Kbps and a range of 30 to 100ft. Each node has a low-power microcontroller processor withspeed of 4 MHz, a flash memory with 128 kB, and SRAM andEEPROM of 4 kB each. The operating system is Tiny-OS, a tinymicrothreading distributed operating system developed by UC-Berkeley, with a NES-C (nested C) source code language (similarto C). Installation of these devices requires a great deal of programming.A comparison of the crossbow motes with that of theUMR/SLU motes is included in several chapters of this book.Mircrostrain’s X-Link measurement system (http://www.microstrain.com/):It may be the easiest system to get up and running and to program.The frequency used is 916 MHz, which lies in the U.S.license-free ISM band. The sensor nodes are multichannel, witha maximum of eight sensors supported by a single wireless node.There are three types of sensor nodes — S-link (strain gauge),G-link (accelerometer), and V-link (supports any sensors generatingvoltage differences). The sensor nodes have a preprogrammedEPROM, so a great deal of programming by the useris not needed. Onboard data storage is 2 MB. Sensor nodes use a3.6-V lithium ion internal battery (9-V rechargeable external batteryis supported). A single receiver (base station) addresses multiplenodes. Each node has a unique 16-bit address, so a maximumof 2 16 nodes can be addressed. The RF link between base stationand nodes is bidirectional, and the sensor nodes have a programmabledata logging sample rate. The RF link has a 30-m rangewith a 19200-baud rate. The baud rate on the serial RS-232 linkbetween the base station and a terminal PC is 38400. Lab VIEWinterface is supported.Radio frequency identification devices (RFID): RFID tags are transpondermicrocircuits having an inductor and capacitor (L-C) tank circuitthat stores power from received interrogation signals, and thenuses the power to transmit a response. Passive tags have no onboardpower source and limited onboard data storage, whereas